Glad we could help :) Just a bit more to do now.
Scan with hijackthis and have it fix the following entries:
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = http://us8l.hpwis.com
O4 - HKLM\..\Run: [checkrun] C:\windows\system32\elitemwb32.exe
O14 - IERESET.INF: START_PAGE_URL=http://us8l.hpwis.com
Then go to C:\windows\system32 and delete elitemwb32.exe
As a precaution, get CWShredder from:
http://www.downloads.subratam.org/CWShredder.exe
Open CWShredder, click on Check for updates, and after it's finished updating, click on Fix.
For every User listed under C:\Documents and Settings, delete the entire contents of these folders (not the folders themselves):
Local Settings\Temp
Cookies
History
Local Settings\Temporary Internet Files\Content.IE5
Delete the entire contents of your C:\Windows\Temp folder.
Delete the entire contents of your C:\Temp folder (if you have one).
Do a search for *.tmp and delete all entries found.
(Note: if any of these temporary files cannot be deleted while in ‘normal mode,’ try Safe Mode.
In addition to SpywareBlaster that Crunchie recommended earlier, you should get:
Ad-Aware SE (http://www.download.com/Ad-Aware-SE-Personal-Edition/3000-8022_4-10319876.html?tag=pop)
Spybot Search and Destroy (http://www.download.com/Spybot-Search-Destroy/3000-8022_4-10289035.html?tag=pop)
Keep them all updated, along with your anti-virus program, and run them frequently (about once a week).
And finally, avoid adult-oriented sites and file-sharing (aka P2P) :)