How do I restore a lost or corrupted Windows .dll file? There has to be an easier way than doing a complete reinstallation of Windows.

Thanks to Tim Swallow, Waverly, Iowa

First, find out what .cab file the damaged .dll file is stored in on the Windows CD-ROM. A .cab file is like a .zip file--it holds one or more compressed files. I'll show you how to restore the file in both Windows and DOS.

To find the file in Windows, insert your Windows CD or Restoration disc; then double-click My Computer, right-click the CD-ROM drive, and select Find (or Search in Windows Me and 2000). Your CD-ROM drive will be highlighted in the 'Look in' field. Type *.cab in the top text field, and enter the name of the missing or damaged file in the 'Containing text' field. Click Find Now (or Search Now, as in Figure 1).

When the search is done, one .cab file should be listed. The file you want is inside that .cab file. To extract it, double-click the .cab file to open the archive as if it were a folder. Find the desired .dll file, and double-click it. In the resulting dialog box, select the appropriate restoration location, such as C:\Windows\System.

If double-clicking the .cab file doesn't bring up anything, consider using CabView, one of the Windows 95 Power Toys. It's available at PCWorld.com's Downloads or directly from Microsoft.

If a damaged file prevents you from running Windows, or if the OS won't let you overwrite the file, restore the old file via DOS. Use your start-up disk to access the CD-ROM drive from DOS.

What? You don't have a start-up disk? Create one now! Select Start, Settings, Control Panel, and double-click the Add/Remove Programs icon. Click first the Startup Disk tab and then the Create Disk button, and follow the instructions.

Put your start-up disk in your floppy drive, click Start, Shut Down, and choose the Restart option. As your computer reboots, you'll see a menu. Select Start computer with CD-ROM support, and you'll eventually see an A> prompt. Above the prompt will be a message with your CD-ROM's drive letter (probably one letter after its usual one).

At the prompt, type x:, where x is the CD-ROM's new drive letter, and press Enter. Type cd \win98 (for Windows 98) or cd \win9x (for Windows Me), and press Enter.

The prompt should now read something like 'E:\win98>'. Type dir *.cab /p and press Enter. When you're prompted to press any key, press Ctrl-C.

The next command is a bit more complicated. Type extract /a /l c:\windows\system topname.cab dllname, where topname is the file name immediately under '..' near the top of your screen, and dllname is the name of the file you need to restore. The command should look something like 'extract /a /l c:\windows\system base4.cab winmm.dll'. When you're sure you've typed it correctly, press Enter.

When the prompt returns, remove the floppy and reboot your computer. Your damaged file should be restored.