I used Dos 7.10 to test xp on different motherboards and now that I settled on the one I want to use I want to remove dos 7.10 or restore windows 98
Previously I had dual boot windows 98/xp and now I have dos7.10/windows xp
I can still get to windows 98 by typing win after I first boot into dos 7.10 but I want to be able to go into windows 98 directly if it's possible
Do I have to mess around with the MBR or is there an easier way ?

It depends on how your dual boot is set up and how you installed the DOS system as to how to remove it.
Is it on it's own partition or is it sharing the partition with W98?