computer is unbootable after dualboot

[dogus]

sorry if this doesn’t belong here, i’m new to these forums and i really need help
today i tried dualbooting windows 7 with windows xp and now every time i try turning on the computer it loads into windows xp, and before it can even start up spits a blue screen that instantly goes away so i can’t even tell what’s going on. i also can’t boot into windows 7 anymore because of the dualboot. i don’t have any recovery disks or anything, only a usb where i installed windows xp to (or at least i thought i did) and removing the usb just doesn’t let me boot at all. how can i get windows 7 back?

 

[samuria]

Welcome to the forum to duel boot you must install the oldest o/s first as it wont have knowledge of how new systems boot. Us Free MR bootable cd to fix it details Fix Boot Problems