Problem reformatting HDD

I need to reformat my HDD, but when I run "format C:" I get the message that the "volume is used by another process. Would you like to force a dismount on this volume? (y/n). I respond yes and nothing happens. I have a 6 year old HP Omni Book with Pentium III processor. I had Win XP Pro SP1 and it had a multitude of problems (viruses, Trojans, etc.) It was also set up to be used in an office with a network, etc. (I don't know if that makes any difference or not). Anyway, I bought new software Win XP Home SP2. It recommends formatting the drive prior to installation. Since I couldn't reformat the drive, I installed it over the old Windows. I would like to know if anyone could help me?

Thanks for your patience. I have already gotten wonderful advice here from reading other threads.

 

Tim:

Thanks for replying. Yes, I did. I was trying to reformat first (my first exposure to PC's was working in DOS). Everything is fine now and I am up and running.

Melanie