Windows 7 Repair Guides Continued.... Back onto the available Repair options. The following is available to you: "Startup Repair" (For when your computer will not boot), "System Restore" (If a problem only started recently then use this to time warp your computer back to a previous state (Say a week earlier) and all should be cured, "System image Recovery" (Restore a backup, if you have one....), "Memory Diagnostics" (Use for random crashes and system erratic behaviour), and last but not least "Command Prompt" (Only use if you know what your doing, this is a manual repair and fixes station, (a wrong command could erase your computer)).
Many useful options as you may agree, always worth a try before formatting your system. A virus scan with up to date software ( AVG Free is a good piece of software) and the same with a good Spyware program (Ad-Aware is another nice piece of software (And is also available free of charge). You may agree that these few steps are worth trying before making any drastic steps that would require a full reinstall of Windows/Drivers/Software/Emails etc etc.