Reformatting help!

[Hopper82]

I am new to this forum and am in dire need of some help reformatting my computer. I am trying to reformat because it is infected with MANY viruses, but have run into a brick wall everytime I think I get it going. I am running Windows XP (an upgrade disk from Windows ME) and when I first started, it wouldn't allow me to get to the setup screen because the version installed was newer than the version on the CD. I remove SP2 and tried again and low and behold was able to get to the set up screen (blue screen with the partitions and whatnot). When I try to delete the C: partition it comes up an error message saying it cannot delete because it is using temporary setup files that are necessary for installation or something like that. I have read many forums on the subject to no avail. My BIOS is in this order: 1st boot device is floppy, 2nd is IDE-HDD, 3rd is ATAPI CD-ROM. I've read a post to change this order to make the CD-ROM first, tried it, and it did absolutely nothing. I then read to change the slave/master order. My primary IDE master is QUANTUM FIREBALLP LM (no idea what this is) and primary slave is not installed. My Secondary IDE Master is Memorex DVD-ROM 16x (my CD-ROM) and secondary slave is LG CD-RW CED-8080B. It is important to note that I recently replaced my CD-ROM about a week ago to the Memorex but installed all the wires to the exact location they were previously (didn't switch any wires from CD-RW to Memorex). This computer is pretty old and is just an extra I have, but I want to get rid of the viruses and reformat to start from scratch. Sorry for the novel and any help would be greatly appreciated