virus prevent copy and paste and svchost error appears

[empire]

i have a great problem,

a virus called teekids.exe Win32:RPCexploit, which prevent the copy paste process and avoid opening links in the internet, sometimes an error message about svshost appears.
notice that i use a windows 2000, when i scan the pc i find a virus in the following path:
C:\Documents and Settings\All Users\Documents\DrWatson\user.dmp
the virus is called Win32:RPCexploit [Trj] Cheval de Troie

i wonder why avast antvirus couldn't prevent a such attack.
thank u very much for your help.

I tried ur solution but the problem still running

[Spiritsongs]

   Hi Empire :

     Because "Trj" indicates this is a trojan, and trojans are
     best removed using an antiTROJAN program, such as
     Ewido Anti-spyware and/or A-Squared . Since you have
     Win 2000, I recommend you 1st try Ewido at :
     www.ewido.net/en .