You could try these two programs:
Kaspersky (anti-virus, has a free trial): http://www.kaspersky.com/
Malwarebytes (anti-malware, free): http://www.malwarebytes.org/
Note that you should only ever have one antivirus program running, so uninstall your current program before installing Kaspersky trial.
screenshot : http://i52.tinypic.com/2dsg3eq.jpg
1. Shut the computer down completely and turn off its power
2. Wait 30 seconds, and then turn the computer on
3. The computer begins processing a set of instructions known as the Basic Input/Output System (BIOS). What is displayed depends on the BIOS manufacturer. Some computers display a progress bar that refers to the word BIOS, while others may not display any indication that this process is happening
4. As soon as the BIOS has finished loading, begin tapping the F8 key on your keyboard. Continue to do so until the Windows Advanced Options menu appears. If you begin tapping the F8 key too soon, some computers display a "keyboard error" message. To resolve this, restart the computer and try again
5. Using the arrow keys on the keyboard, scroll to and select the Safe mode with Networking menu item, and then press Enter. The computer should boot in Safe Mode.
Once in safe mode, try installing as normal.
To leave safe mode just reboot the computer normally.