Since you are going to use that machine for business, you won't need much of what is on it now. You will especially hate Vista.
First boot the machine while tapping the delete key. That should take you to the BIOS. The opening page of the BIOS will list the drives. Make sure the macnine is seeing the hard drive.
Then go to your local community college bookstore and buy a copy of Windows 7 PRO for about $100. (Student discount but they usually won't ask you for a student ID) Then do a clean new install.