"multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect"
from your boot.ini and goto you diskmanager and delete the partition (2). If you have files on that partition I recommend backing them up. Once the partition is deleted then right click you primary partition and select Expand Partition to encompass the remaining space.
If you have never done this before I recommend you back every thing up because there is potential you will wipe every thing out.