Sweden here! My company needs to upgrade Servicepack on all computers to SP6a. On some computers i get the error message: "the program cannot determine whehter you run Windows NT Workstation or Windows NT Server" and then refuses to upgrade.
What is wrong? This happens on pc:s with SP5 and SP6

Unless there's something going on at Microsoft-Sweden that I don't know about, Service Pack 6a is Service Pack 6.

The other issue is that you need to disable as many services and devices as possible before you apply any service pack, and you should remove all previous service packs before applying the new one.

Follow this link:

http://www.labmice.net/ServicePacks/articles/survivesp.htm

Or, better still, this one:

http://support.microsoft.com/default.aspx?scid=/support/servicepacks/WinNT/4.0/SP6a.asp

The Server vs. Workstation issue will have to be addressed by another forum participant. That's an error message I've never seen.