Here's some maintenance steps to be going on with.
The ones that are specific to the adware are near the bottom, but everything is worth doing regularly.
General system maintenance includes:
Defrag
FULL patching
Virus scanning
Spyware scanning
removal of rubbish files
Defrag is an inbuilt function in XP.
OPen My Computer > Right click C: > Tools Tab and its there.
To make sure everything is running fine run both anti virus and anti spyware apps in
normal AND safe modes. (make sure that they are updated first !

) (
AVG is good and free AV)
(A couple of good spyware removal tools are
Spybot and
Adaware)
ALso an on line virus and spyware scanner is
Trend Housecall
Just a note; actively running two AV's on one machine can cause problems.
So if you are thinking about it make sure your current one is disabled first.
SAme thing applies to online scanners as well.
Removal of junk files is easy with
CCleaner a free app that does exactly what you neeed.