Hardware & Software

Assuming you want to remove a partition other than the boot partition, right click on My Computer and then Manage. Go to Disk management under Storage. Right click on the desired partition and click delete.

Now, do you simply want to remove a partition?
Or, combine 2 partitions into 1 large partition?

If you want to delete a partition, Run Administrative tools, computer management, and select disk manager.

Right click on the partition that you wish to remove.
CAUTION: removing a partition deletes ALL files.

CAUTION 2: If the partition you wish to delete is the boot drive, Windows will not load if you delete this partition.

If you wish to combine 2 partitions into a single larger partition, you need a 3rd party utility such as Partition Magic.

For XP, you need the latest version. Verify that the software you buy has NTFS support.

CAUTION: Even though you should not loose any data, it is BEST practice to back up your files before running ANY partition manager.

Chas

While the previous answers are good and may provide the results you are looking for I think most would agree that providing an answer to a question such as this leaves open lots of variables and we have to assume many things here.
If you don't careabout any of the data on any of the hard disks/partitions in your PC or if you have a good back-up go ahead and give it your best shot it's not that difficult to understand and this would be a good time to learn. If you have ANY critical data on ANYhard disks/partitions that you care about be sure you have a good back-up or source to restore from before attempting such tasks.

Try and use Partiton magic if you have this, very useful in removing unwanted partitions.