Check these links for online virus scanners. It's recommended to run at least two of these.
Norton/Symantec --> http://security.symantec.com/sscv6/default.asp?productid=symhome&langid=ie&venid=sym
Trend Micro --> http://housecall.antivirus.com/housecall/start_corp.asp
Panda ActiveScan--> http://www.pandasoftware.com/activescan/
Stinger --> http://download.nai.com/products/mcafee-avert/stinger.exe
These links Check for Spyware:
Spybot-S&D --> http://www.safer-networking.org/
HijackThis --> http://www.spychecker.com/program/hijackthis.html
Web Shredder--> http://www.spywareinfo.com/~merijn/cwschronicles.html#cwshredder
Pest Patrol --> http://www.pestpatrol.com/downloads/eval/download.asp
PCHell removal->http://www.pchell.com/support/spyware.shtml
Make sure that after downloading these, that you update them. It helps to try at least two of these.
If all else fails, download HijackThis and post the log that is generated after running it on your system.
Try the System File Checker:
Click Start->Run->SFC <enter>
(see: http://users.westelcom.com/rogersr/sfc.htm
http://support.earthlink.net/mu/1/psc/img/walkthroughs/windows_9x_nt/dialers/dun_1.3/0850.how.to.sfc.psc.html)
Removing items from Startup:
Click Start->Run->MSCONFIG <enter>
In the Startup tab, start out by disabling everything you're unfamiliar with (or everything if you're unsure).
Click Start->Run->Regedit
*Be careful when editing the registry as an accidental deletion can render your system inoperable.
First navigate to the following key in the registry:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
*You might also find RunOnce, RunOnceEx, RunServices, RunServiceOnce or any of these with a trailing dash (-)
Once found, click File, Export to save a copy of the key before you delete any items (if necessary).
After the file has been saved, delete items as needed from the right pane.
Now find the next startup key:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
*You might also find RunOnce, RunServices, RunServiceOnce or any of these with a trailing dash (-)
Follow the previous procedures to export a copy before deleting items from the right pane.
Remove temp files from your system on a periodic basis:
Click Start->Run->%TEMP% <enter>
This is the temporary folder location. All files can be deleted here, but not the containing folder.
Some files may be in use, so an error may be generated but can be ignored.