Reinstalling your Windows and software programs is sometimes the only way to return your computer's stability and performance. Over a period of time when programs are installed and uninstalled, many files get overwritten and some get corrupted. It is also the only sure way to eradicate a virus.

The procedure I use for reinstallation is to first partition the hard drive if only one partition exists, so that a new backup partition is created. This will then become the "D" Drive. Clients' data, files and folders such as documents, mail settings, messages, image files etc. are then backed up to this new partition.

The "C" Drive is then formatted clean and windows reinstalled. Updated drivers are downloaded from the Internet as necessary. Clients' backed up files are then reinstated and the operating system configured for optimum performance.

The final stage is to create a backup image of the "C" Drive and save it on the "D" Drive, returning the computer to this optimum state is then reduced to a system format and restore of the image.

The backed up data files on the "D" Drive can be kept updated and restored easily if in the future a system restore from image is necessary.

Take a look here to see what is involved in reinstalling windows. Ref. Backup