|If you want to reinstall Windows 7 and do not care about anything that is on the drive (anything on the drive will be lost by this method) use the installation/Upgrade DVD and you choose Custom and Partition/Format, then Delete the current Partition that is your C drive (and any others you do not want), RePartition and Format. Then you can proceed with a completely clean installation.|
If you have any problems, it is probably time to test your hard drive and memory for problems. Use the hard drive mfg's utiltiy to test it and Memtest to test the memory. Use the bootable CD method since it will not matter if you do not have a working operating system installed when you test them.
You have to be a little bit crazy to keep you from going insane.