When dealing with spyware you have to run multiple apps to reliably clean any infections. none of them catch everything and some can disable or evade scanners when those scanners are installed and executed on a compromised system not running in safe mode.
APPLIES TO WINDOWS XP:
FOLLOW BELOW PROCEDURES CAREFULLY AND MAKE BACKUPS OF ANY DATA YOU DO NOT WANT TO LOSE FIRST. IF BACKING UP DATA YOU WILL NEED TO SCAN IT FOR VIRII AND OTHER MALWARE, SPYWARE ETC. BEFORE PLACING IT BACK ON YOUR HARD DRIVE
If you think you might have a spyware infestation there is only one way to clean the hard drive and you need several utilities to do it.
First though turn off system restore on all drives and remember to not use and restore points made prior to this cleaning procedure unless you want to reinfect yourself. Then go to Add/Remove programs and uninstall any obvious spyware related entries listed. This is normally items like Search Bar and other related items. It is needed. Doing the above will prevent any "stuck" entries in the add/remove list after you power force the badies off in the following procedures.
First you need to obtain Spybot Search and Deystroy, Ad-Aware SE and Microsoft Malicious Software Removal Tools. Place these in a folder on the ROOT drive that is to say your main hard drive C: and not in any of the profile directories under Documents and Settings. You also need to get the manual update files for both of those and place them in the same directory. Do not attempt to install them on a potentially compromised PC not running in safe mode. Then you need to get Hijack This!, kill2me, bholist, CWShredder and Cool Web Mini remover and place all of those in the same directory. Finally download a copy of Avast! Anti-virus Home edition and the manual definitions update file for it and save it to the above listed directory you have just created.
Now reboot and hit F5 before windows loads to get to the Boot options screen and select Safe Mode. Once into safe mode hit ctrl-alt-delete and make sure there are no bugs or exe's running except for your basics. Run Hijack This! and save the log file to your newly created directory on the root drive. Now install Spybot and do the update file then run it. Clean all that it finds. Then do the same with Ad-Aware and clean all that it finds. Then do the same with the Malicious Software Removal Tool and let it clean what it finds. Now run Hijack This and save that logfile under a different file name than the first hijack This log and place it in the same directory with your removal tools.
When looking at your Hijack This file it helps to have internet access on another pc somewhere in the vicinity to use google search to research all the executing processes and items revealed by Hijack This. Now run CWShredder, kill2me and cool web mini remover. Finally install Avast anti-virus and do the manual update then say yes when it asks if you want to run a boot time scan on the next reboot. Now reboot and let it scan and clean anything it finds. I would select to quarantine anything you find as opposed to deleting until you are sure you are not going to trash the system.
Now boot in normal and run Hijack This again to get a capture of what is running. You should be clean by now. If you are missing any .dll's or anything becuase of legitimate files being taken over or replaced by badies search for them on google and reinstall them. They normally reside in your system32 folder.
Hope this helps.
Of course if you don't have any data and you have a valid operating system cd with valid key it may be easier to just wipe the drive, repartition and format that drive then reinstall windows.