After running scandisk and defrag you should clean your system with the following if you are not already using them.
Download & install CCleaner from here: http://www.ccleaner.com/
1. Run CCleaner using it's default setting's by clicking on "Run Cleaner".
2. A popup box will open advising the process will permanently delete files from your system.
3. Click "OK" and it will scan and clean your system.
Download & scan with Ad-Aware SE 1.06: http://www.lavasoftusa.com/support/download/
Setup & Configuration instructions: http://www.bleepingcomputer.com/forums/ind...showtutorial=48
Download & scan with Spybot S&D 1.4: http://www.safer-networking.org/en/index.html
Setup & Configuration instructions: http://www.bleepingcomputer.com/tutorials/using-spybot-to-remove-spyware/
After scanning run Spybot in Advanced Mode, click on Tools and scroll down to System Startup to see what programs are loading when Windows starts.
Many applications install themselves to run at startup but are not required for the program to work. Disabling them can save system resources and improve overall performance. If your not sure what they are or if they are required then search the Startup Database:http://www.bleepingcomputer.com/startups/
You also may want to run one or both of these online Virus scans:
Panda ActiveScan: http://www.pandasoftware.com/products/activescan.htm
Trend Micro Housecall: http://housecall60.trendmicro.com/en/start_corp.asp?id=scan