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August 10, 1998

Crash! Take advantage of these emergency Registry routines if Windows goes south

In this week's column, I get the opportunity to describe a little-known new feature of Windows 98, explain how to do somewhat the same thing in Windows 95, and offer a bit of errata for my book Windows 98 Secrets.

Since the days of Windows 95, the Windows Registry has taken on more and more importance. The Registry file (two files, actually) took over most of the roles of the old Win.ini and System.ini configuration files found in Windows 3.x.

Because of the importance of the Registry, Win95 creates backups of System.dat (which contains information about your hardware) and User.dat (which preserves your software preferences). These backups are named System.da0 and User.da0, respectively, and are created every time Win95 successfully starts.

If your system somehow corrupts the Registry, you can theoretically copy System.da0 over System.dat and User.da0 over User.dat to get back to a previously working state. One flaw in this theory is that most users reboot Windows when they encounter a serious problem. In this case your one good copy of the Registry is overwritten with a buggy copy when Win95 loads.

In an attempt to give power users a tool to preserve several backups of the Registry, Microsoft included an Emergency Recovery Utility (ERU) on the Windows 95 CD-ROM. The ERU creates an emergency boot diskette with a copy of your Registry and several other configuration files, such as Config.sys.

Read the Eru.txt file found in the \Tools\Misc\Eru folder of your Win95 CD for details. Copy the four files you find in that folder to your Windows 95 folder, then create a shortcut for Eru.exe and run it. If you don't have an emergency start-up diskette for Win95, make one right now. If your hard disk won't boot up (it's only a matter of time), boot from the floppy and you may be able to get your system back to normal.

Win98 improves the security of your Registry by making not one, but five separate backups. These backups are compressed into "cabinet" files called,, and so on in your \Windows\Sysbckup folder. On my system, each consumes about 1MB.

These backup files are created automatically when you start Win98 (but no more than once per day). Win98 runs a program called ScanReg using the command line scanregw/autorun. You can create a backup with ScanReg anytime you wish (for example, before you install a new program or manually edit your Registry). To do so, click Start, Programs, Accessories, System Tools, System Information, Tools, Registry Checker.

If you somehow corrupt the Registry in Win98, you can choose to restore one of the previous five backups. Unfortunately, there's nothing in the manual you get with Win98 that tells you anything about this.

To restore a backup Registry, you must hold down your Ctrl key while your system's power-on self-test is running, then choose Command Prompt Only to get to a DOS prompt. You then type scanreg/restore to run the DOS version of ScanReg. This presents you with a list of backups and their dates so you can choose one.

The process is controlled by a text file called ScanReg.ini in your Windows folder. Open it in Notepad and read the simple documentation. You can edit ScanReg.ini to increase the number of backup copies Win98 saves (as many as 99 if you're paranoid) and specify other files (such as Config.sys) for ScanReg to back up along with the Registry.

Here's where the errata come in. Microsoft included both ScanReg and ERU on the Win98 beta CDs but dropped ERU from the final CD-ROM. The final CD came out after my co-author, Davis Straub, and I had already included a section on ScanReg and ERU in Windows 98 Secrets. Sorry. Just ignore the part about ERU if you're using Win98, and we'll take it out in the next printing.

DLL update

I'd like to thank the hundreds of readers who have sent me tips about Win98's setup routine and its effects on non-Microsoft applications after my recent columns on the subject. I've read most of your comments by now and will report on them again soon.

Brian Livingston's latest book is Windows 98 Secrets (IDG Books). Send tips to He regrets that he cannot answer individual questions.

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