Free DOS is a free alternative to MS-DOS, which most Laptop/Desktop manufacturers bundle with most of their cheaper offerings. AFAIK, it's not a headache at all installing windows 7 over a system shipped with Free DOS as all you have to do is have a legitimate copy of the OS you want to install (preferably in a DVD, USB drives also work on newer systems), change your CD/DVD Drive as the primary boot device from Boot Menu of your BIOS and insert the installation media and boot from it to install the OS. You can simply format/delete the already available HDD partitions.