Problems with Windows XP update, SP3, & Antivirus software?

[doowopper]

I am using Windows XP with Service Pack 3 in a Dell computer.

Tonight F-Prot antivirus software removed several files and quarantined several other files that were infected with a virus. In the F-Prot quarantined file list, it the following file was quarantined twice today: "asyncmac.sys."
1) What does asyncmac.sys do and is it critical for Windows' XP stability?

After F-Prot removed or quarantined several files, a window appeared stating that I need to put the Service Pack 3 cd in the cd drive to replace certain files that were removed or quarantined. And, if I didn't do it, Windows might become unstable.
2) Is there a way to determine if Windows XP is now unstable - that is, determine Windows stability before it potentially crashes?

Since I do not have a Service Pack 3 cd, I couldn't follow the above instructions to use a service Pack 3 cd to replace the files that were quarantined or removed by F-Prot. So, I then thought about trying to reinstall Service Pack 3. To reinstall Service Pack 3, I clicked on the Windows Update icon which took me to a window in Internet Explorer 7 that stated, "Files required to use Microsoft Update are no longer registered or installed on your computer." So I chose, "Register and reinstall the files for me now," in that Window. When I then clicked on the "Continue" button, that same window just kept reappearing and I could get beyond it to a page that would allow me to update Windows XP or download Service Pack 3.
3) How do I fix that Windows update page so the required files for Microsoft update are installed on my computer?

4) How do I download Windows Service Pack 3?

5) Given the problems mentioned above, should I reinstall Windows Service Pack 3?

Thanks.
Richard

[nuz]

3. Check the links, on the MS updates page. There should be an option for network admins to d/l installers. It's larger than the one you'd get with windows update, but you can burn it onto a CD in case you ever have this problem again.

4.
http://download.microsoft.com/download/d/3/0/d30e32d8-418a-469d-b600-f32ce3edf42d/WindowsXP-KB936929-SP3-x86-ENU.exe
Should still work.

[Paul Komski]

@nuz
Try to avoid direct download links. If possible post the link to the download page and let peeps then make their own decisions.

The Microsoft Downloads area is different than the MS Update area and a number of download options for SP3 are available (http://www.microsoft.com/downloads/en/results.aspx?freetext=sp3+network&displaylang=en&stype=s_basic).

[nuz]

I had the link left over from when I d/l-ed SP3. Just copied and pasted off fdm.

[Paul Komski]

I was not saying you should never post direct links - just that it is something best avoided if possible.