Go to administrative tools -> computer management
(Sorry if it does not match exactly with english, because I am translating from my Portuguese W2K).
Opening the computer management, go to storage -> drive management
You will see all your drives and partitions. Right click on the drive you want partition and format.
When formatting, you can select the file system you want (NTFS, FAT32 or FAT) AND THE MOST IMPORTANT: THE CLUSTER SIZE.
With higer cluster sizes, you will have a better performance, but the slack space will increase. Small clusters mean more clusters to be read to fully assembly the file.
I prefer a big cluster (something like 16k, 32k or even 64k) for better performance.
I dont care for slack space... HD prices are low today. It is better to buy a new drive...