How do I completely clear my computer's hard drive like it was brand new?

I have so many virus's and crap on my computer and i'm about to start a new business. How do i clean my computers hard drive so that i can re download all my programs? I have my the software that came with my computer when i bought it to put back on it when i'm ready. I have Drivers and utilities, Operating system. Is there anything more i need? How do i get started? I don't know allot about computer!How do I completely clear my computer's hard drive like it was brand new?
The steps iam giving you should go under some supervison


You have not mentioned that operating system you have.





First you must have a startup or boot disk so that you can load your PC and work on Dos.You can't format your operating system drive while working on it.


Startup disc can be created by using Floppy disc with win 98 or ME or 2000.If you don't have any of these then borrow it from some friend.





once get the floppy or boot CD then insert it and restart your Pc. normally it should take external drives as first boot device and give you a A :(prompt). Now type X: where X is the drive you want to format.





Then format x: where X is the Operating system drive.


It will say all data will be lost. you can click Y and enter and it will format your drive. Now you have No OS on your PC.Insert your windows CD and restart the PC . It will boot automatically and start the installation.





2nd method .





Run WIN XP CD directly from your CD rom ann follow the instructions. do a new copy installation . I think it will format the OS drive automatically .(iam not sure about this). I did it through win 2003 server installation not sure of XP.How do I completely clear my computer's hard drive like it was brand new?
You have to reinstall Windows and format the disk during the installation. Then you are back to square one, with everything fresh. You'll need the Windows installation CDs.