Partition with Linux

I think I have messed up this hard drive as I do not know anything about linux. Anyway a 40gig seagate had been partitioned (by someone else) into three partitions. Middle one being linux. Not understanding Linux I fdisked and formatted the hard drive. Installed XP Pro. but noticed a lot of little problems, installing programs, defragging, usb devices. Tried re-installing but same thing. I put it down to this mid partition having Linux in it and not removing it properly. I have since been told that you need Linux to remove it and that DOS would not have recognised the partition. Okay, can I undo my mistake and how, thank you.