theres tons of things you can do before deleting all your data.....
is the hard drive light on or flashing during this time? if so...
d/l a program that can show you all of the startup programs and disable things you don't need. run 'services.msc' and disable what you don't need. (do your research first so you don't disable something vital). you can try defragmenting the hard drive. you can d/l a program that fixes invalid registry entries.
is the hard drive light off during this time? if so...
you might be f'ed in the a'. this could be a hard drive problem. try d/ling another utility called hard drive diagnostic or something like that. it'll analyze the state of your hard drive and its mechanical parts and give you a somewhat accurate view of it's state.