Hey man, you can format your drive without multiple partitions. All you need is a Windows 98 startup disk. Tell it to boot into DOS mode and use the command: format c:
This should format your drive successfully. Lone Wolf your help only applies to someone who in fact does not want to format their main partition. And yea, you can't format the main windows partition while it's still running.
BEWARE: ALL FILES WILL BE LOST, INCLUDING YOUR WINDOWS INSTALLATION. You will need to reinstall windows following the format of the main windows partition.
There are also easier ways in providence of software. Partition Magic can perform many amazing things with a hard drive reguarding partitions, but if your only going to format, just use a windows 98 startup disk and save some cash. If you have XP you can't make one your-self, as a new add/remove programs system was developed without it's oddly placed Startup Disk creation utility, however, you can find various places to download the files manually.
You can also use your NT/2000/XP installation cd to format your drive. There are many options and possibilities, and it's your job to explore them. My favorite and more appreciated format method is with the startup disk.