read this
http://www.sophos.com/virusinfo/anal...2forbotay.html

under the description tab you'll see

W32/Forbot-AY attempts to spread to network machines using various exploits including the LSASS vulnerability (see MS04-011). The worm may also spread via IRC channels.
next
http://www.microsoft.com/technet/sec.../MS04-011.mspx

From Microsoft
Microsoft Windows 2000 Service Pack 2, Microsoft Windows 2000 Service Pack 3, and Microsoft Windows 2000 Service Pack 4 –

whlie you said that you had only updated to service pack 2 GET THIS SPECIFIC PATCH HERE
http://www.microsoft.com/downloads/d...displaylang=en

get your computer scanned online at
http://housecall.antivirus.com

eventhough you said your computer cannot take over service pack 2.
I STRONGLY RECOMMEND YOU DO.