Is it hard to install a new Windows system and completely wipe out the old program?

Not at all. All you need is a Windows Installation disc. Put it in your computer, and it should boot from the disc. At a certain point, it will ask you which volume you wish to install it on. Simply tell it to delete the current volume, then format it as NTFS or FAT (I prefer NTFS usually, but FAT has its advantages), and then install it to that volume.