You can't format without partitioning first!
I'd be cautious about wiping whatever's the on the drive and starting anew.
- If your laptop came with a genuine Windows CD (Windows XP, Vista, whatever - it'll be holographic), then you're probably good to go.
- If it came with a recovery CD (basically the manufacturer's "bundling" of Windows with apps and drivers so that it only works with that specific model) you may or may not be set to go. I don't know what partitioning options are available from recovery CD's - if they let you partition, or if they wipe everything when doing a recovery and only partition their own way (no customizations possible).
- If it didn't come with any of those you may have a recovery partition on the hard drive. It may be hidden or not. On some computers (HP I think) you can access the recovery partition from the BIOS to restore your system to factory settings. Of course if you accidentally wipe that partition, you won't be able to do any recovery (although some manufacturers will mail you a recovery CD/DVD for a fee if that happens).
If you have your own full version or upgrade version of XP or Vista, then I guess it doesn't really matter, but you might be unable to use the product key (which is an OEM key) that was bundled with the laptop if you wipe the recovery partition.
But to get to practical matters:
If you boot into either the Vista or XP CD, and follow regular install procedures, you'll be able to partition your drive during setup. In XP it looks like this:
http://www.sumedh.info/pictures/inst...ion-format.png and on Vista it looks like this:
http://clientsupport.stonybrook.edu/...SelectDisk.jpg
If you want to partition manually before running setup, boot from your XP CD or Vista DVD, then go to repair (press R for XP, click repair for Vista) and enter the recovery console (command prompt on Vista). Then type diskpart and follow the instructions from there (Vista's diskpart is a tad harder to use than XP's, but you can type help at any time if you're lost).