640x480 16-color VGA blank screen

[jimraehl]

I have WIN98SE using SiS Mirage graphics on the motherboard, on one of two hard disks. Originally, I installed WIN98SE fine on both drives, then installed WIN2000 PRO over WIN98SE on one. VGA video worked fine in all resolutions when booting from both drives.

Sometime after, the DOS window came up blank in fullscreen mode on the WIN98SE disk. I uninstalled the SiS drivers, to reinstall them and hopefully clean up the blank screen. Windows installed its VGA driver. Upon reboot, I had a blank screen in Windows. Apparently, Windows VGA defaults to 640x480 16-color mode, which now has a blank screen. Safe mode does display, in some lower resolution. WIN2000 on the other disk still displays fine in all respects, including DOS full-screen mode.

The only thing I can think of that might have clobbered 640x480 16-color was a Windows Update device driver update for the display. However, that caused a problem (don't remember what). I reinstalled the SiS display drivers from the motherboard CD-ROM.

I tried to reinstall the SiS drivers in WIN98 safe mode, but Windows doesn't see the CD-ROM drives.

I would ideally like to at least install the SiS VGA drivers. Preferably fix the VGA problem too. I tried reinstalling WIN98SE to the first restart, but it apparently only did a refresh. All the software installs are still there. I think I found a thread here to force a full WIN98SE install, but shudder at losing all the software installs. I've lost some of the software install CD-ROM's.

Now the questions:
1. Is there a way to boot into WIN98 safe mode with CD-ROM available. The CD-ROM drives are not showing in safe mode.

2. What happens if I remove the Windows VGA driver, leaving no VGA driver. Will Windows display in the safe mode resolution without the VGA driver. Obviously, if the VGA driver is required and I remove it, I cannot bring back the Windows VGA driver without a visible CD-ROM drive.

3. The Windows VGA driver in Control Panel > Display only shows a single resolution, 640x480 16-color. Is there a way to force some other resolution.

4. Any ideas on what is clobbering 640x480 16 color display. Device manager in safe mode showed the Windows VGA IRQ at 0, instead of expected 11. Setting it manually to 11 didn't fix the blank screen.

5. Is there a program somewhere that displays current usage of IRQ's and device address locations. Maybe I can spot a VGA conflict that way.

[glc]

Boot it up into 2000 and copy the driver install from your CD into a folder on your 98 partition. Then you can try to run the install in safe mode. There are 4 different Mirage chipsets, so if your CD has drivers for more than one version, make sure you use the correct one.

[jimraehl]

Thanks. I have an SiS741, per the WIN 2000 ID. I was able to start setup.exe in the Sis661 folder, which includes 741. However, setup aborted with a message that it couldn't detect the VGA hardware. Apparently WIN98SE safe mode prevented the detection. Didn't see that problem in WIN2000 regular mode, when I tested the same setup.exe.

I tried to find something in setup.ini which would force installation for a specific adapter. Didn't find anything that worked.

For fun, I renamed VGA.DLL in WIN98 safe mode. Windows safe mode died upon restart. IMHO that answered the question about removing the VGA driver. Has to have a VGA driver.

I may have to buckle down and reinstall Windows 98 after all.

[jimraehl]

Backed up Windows, then started to reinstall Windows. Checked for VGA problems as I went. Stumbled onto the culprit that was clobbering the 640x480 16-color VGA. It was the AVG anti-virus boot virus-check program in autoexec.bat, line c:\Program Files\AVG Free\bootup.exe. Restored the original Windows directory and reloaded the SiS VGA drivers. Back to normal, without that boot program.

What is peculiar is that the boot program worked fine on my old computer with a different motherboard. The new computer has a PC Chips board.

The AVG boot program was apparently wiping out not only 640x480 16-color mode, but some others as well. Several color depths and resolutions appeared in Control Panel > Display, after I removed bootup.exe from autoexec.bat.