When I try to install the SP4 for Windows 2000, I get this error message: "The file c:\winnt\system32\drivers\atapi.sys is open or in use by another application. Close all other programs and click retry." What can I do to solve this??? Please help

That sounds like maybe you have drag to disk running. You should shut down all background tasks when doing any updates, installs, etc. At the very least, close all programs in the tray.

I also had probs with SP4, the most stable SP was SP3 imho

I am running SP4 with no problems.

many millions of people are running sp4 with no problems. this does not mean anything. all i said was that i thought that sp3 was the most stable sp. millions more people are running win2k without any sp.

Most folks with modern hardware need some service packs to run the hardware. DX9 can't be installed until one of the service packs is installed, can't recall which one. The 137GB limit is another issue, as is USB 2.0. I agree with you in the sense that if you don't need it, don't update. The problem is, most of us DO need it. There is the other school of thought that jumps to use whatever comes along wheather necessary of not. Like flashing the BIOS when no problems are present.

I had this issue too, and I found a solution. The problem is, atapi.sys is modified and/or locked by some program handling virtual drives (daemon, alcohol, ...) I had alcohol on my desktop, and uninstalled it as starters... maybe you could try the next steps without doing this... who knows ? search your system drive for atapi.sys (be sure to display hidden+system files) you should see two entries: \WINNT\system32\drivers\atapi.sys \WINNT\system32\dllcache\atapi.sys if you can see only one, put your win2K install CD in your CD-drive (cancel autostart) start command propmt. type "sfc /scannow" this will restore the driver cache with original files. then re-do the searching (atapi) from the search window, right click each file and open each folder containing them. copy the one in "\dllcache" and paste to "\drivers" (overwrite) now try and install sp4 again (no reboot needed) then you can try reinstall software... (I didn't right now) ;)