Do all this stuff.
Tune-Up and Clean-Up
First Ccleaner http://www.piriform.com/ccleaner
Then Malwarebytes http://malwarebytes.org
(Or just update and run your current Virus Scanner)
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Run Error Checking
Right click on C: in (My) Computer
Properties
Tools
Check box for Error Checking
Reboot
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Run Disk Cleanup
Right click on C: in (My) Computer
Properties
Disk Cleanup button
After it Calculates how much space you can recover,
Click on the More Options Tab then
System Restore Cleanup Button (this can recover a lot of space)
Windows 7
Clean up System Files Button
More Options
Clean up under System Restore and Shadow Copies
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Control Panel
Add/Remove Programs
Look at Programs you no longer use and uninstall them. ie Trialware and programs you installed but don't use anymore.
(Don’t if not sure - windows will say you have not used it in a while but it may be an important program)
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Right click on C: in (My) Computer
Properties
Tools
Disk Defragment
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Consider doing a Recovery to Factory Condition.
Type the word RECOVERY in Start/Search field.
Follow manufacturers instructions.