To start fresh, you can't just delete and then reinstall Windows 95 and all your software. Persistent PC problems sometimes stem from a damaged File Allocation Table (the table of contents that Windows 95 uses to locate files or specify damaged sectors on your hard disk). ScanDisk or a similar disk utility will let you know when your FAT's in the fire: Clues include problems with file names or folder names that can't be fixed by running ScanDisk, and files or folders that won't open or can't be deleted.

To fix such problems, you reformat the disk ù either physically (a low-level format) or logically (a high-level format).

A low-level format (first done at the factory) draws magnetic lines on the hard disk. Fortunately, these days you rarely need to redo a low-level format.

A high-level format creates a new FAT and scans the surface of the disk, finding and marking damaged sectors (those that won't hold data). Performing a high-level format is deceptively easy; simply run format.com in DOS or the Format utility (by right-clicking the drive icon in Windows 95 Explorer). But this wipes out everything on your drive; so before you try it, make sure you're out of other options.

Here's one final alternative. Try moving your current installation of Windows 95 and other software to another hard disk (if you have one) or to a second partition on your current hard disk. Of course, the partition or second hard disk must have enough free space to hold all your files. Once you've done this, you can reformat the suspect partition and use it again. You can even move the operating system and your files back to the original partition.

To resize an existing partition or create a new partition without losing any data, use a utility like PowerQuest's PartitionMagic or Quarterdeck's Partition-It Extra Strength. Make the new partition a primary (not a logical) partition, since only primary partitions are bootable.

The next step is to make the target partition or second hard disk bootable. First, add the system files by opening a DOS box and typing sys d: (or the correct drive letter). Now set the target partition as the active, or boot, partition, using the DOS fdisk command (see Repartitioning your drive saves space and trouble, June 98, p170) or a utility like Partition Magic.

Finally, copy all but one of the files to the new partition, including those marked as hidden. (The exception is win386.swp, the swap file.) Go to Explorer and select Show all files under ViewûOptions (or ViewûFile Options with Internet Explorer 4.0 or Windows 98). Then select the Windows folder in Explorer, and hit <Ctrl>-A to select everything. Run down the left window, and find win386.swp; deselect it by holding down <Ctrl> and clicking the filename. Now copy everything else to the target partition.

Repeat this process to copy all the other files and folders, making sure that you deselect the Windows folder you just copied. If the target partition is on the same drive as the original partition, you should be able to restart, and Windows will load from the new partition. If you've copied Windows to a second hard drive, you must swap the connections on the two drives and possibly also switch their master/slave jumpers.

Partitioning won't do it? OK, time to reformat your entire drive.

This will blow away all the data that's stored there, so save everything you need:

Windows 95 installation files. Make sure you've still got your Windows 95 CD or floppies. And find the correct registration number; Windows 95 setup will ask you for it. It's usually posted on a green certificate that comes shrink-wrapped with the Windows 95 manual.

If you purchased the upgrade version of Windows 95 and installed it over Windows 3.x or DOS, you'll need your old program disks as well.

Configuration files and drivers. Back up the old DOS and Windows 3.x configuration files: autoexec.bat, config.sys, win.ini, and system.ini. When you reinstall Windows 95, the software will install the appropriate Windows 95 drivers.

But older devices in your PC may be running on older DOS or Windows 3.x drivers. If you find that your PC is using an older driver for a certain component, this is a good time to check with Microsoft or the component manufacturer to see if a new Windows 95 driver has been written since your last Windows 95 installation. Updating drivers is usually a good idea ù especially if the upgrade involves switching from a DOS driver to a Win 95 driver.

If you do have to reuse your old drivers, make sure you back up the actual driver files as well as the configuration files that launch them. To be safe, back up all the files in a driver's folder, not just the file named in the configuration file. That goes for any hardware you installed after installing Windows 95. If you don't have the disks, hunt for the files on the hard drive.

Windows 95 Startup Disk. This is a bootable floppy with all the utilities you'll need to reformat your hard disk. In Control Panel, double-click the Add/Remove Programs icon, click the Startup Disk tab, and then click the Create Disk button to make the disk. In addition, you'll want copies of DOS's xcopy32.exe and xcopy.exe files.

If you plan to reinstall Windows 95 from a CD-ROM, you need a copy of your PC's DOS CD-ROM drivers on the Startup Disk, plus copies of autoexec.bat and config.sys with the command lines that call those drivers. If you don't have those last two files, search your hard disk for auto* and config*.

Put your DOS CD-ROM drivers on a floppy

Caption: To reinstall Windows 95 from a CD-ROM, you must first create a floppy disk that will enable the CD-ROM to work properly

Application software installation materials. As with Windows 95, you should have all the installation disks or CD-ROMs and all required serial numbers at your fingertips. Don't forget to copy any software you've downloaded from the Internet, too.

All files you want to save. Back up your data to another hard drive, a network file server, a Zip drive, or another PC via your parallel port ù or in the worst case, in compressed form to floppies.

Anything else of value. Once it's gone, it's gone. So back up anything you might someday regret losing ù including crucial settings information. If the PC is on a network, record all your network parameters (double-click the Network icon in Control Panel). If you do Dial-Up Networking, write down all the connection settings. And for good measure, crank out a system resource report and look it over for files you may have missed. (To make a printout, go to Device Manager, click the Print button at the bottom of the screen, and under Report Type select All devices and system summary.)

Caption: A system resource report helps pinpoint the drivers you must back up

Before you run the format command, reboot from the Windows 95 Startup disk. At the A:/> prompt, confirm that your DOS CD-ROM drivers are properly installed by putting a CD-ROM in the drive and typing dir d: (or whatever drive letter is correct). A list of the CD-ROM's files should appear.

To format your disk ù or the partition where you plan to reinstall Windows 95 ù type format c: /s and press <Enter>. (Substitute an alternative drive letter if appropriate.) The /s switch will copy all the system files necessary to make the drive/partition bootable and ready for Windows 95 installation.

Insert the Windows 95 CD-ROM, type d:\setup (substituting your CD-ROM drive letter), and press <Enter>. The installation program will launch at once. Windows 95 will poll all your hardware and install drivers from the CD-ROM. Once Windows is running, you can install more recent drivers ù or hardware Windows 95 didn't recognise ù by double-clicking the Add/Remove Hardware icon in Control Panel.