Dual boot windows xp and win 7 64-bit

I've set up a multi boot system before, installing the older OS first (xp), then the newer one after (vista and/or 7). And all went well. However I have this 1 game that just will not run in windows 7 64-bit (ran fine in the 32-bit RC). I'm attributing this to the video drivers. It's an ATI FireGL. There are no official release drivers other than the ones windows7 installs during installation. like i said, the game worked fine in the 32 bit release candidate i was using until it expired. So anyway, I've tried xp mode, Virtual box and no go. So i decided to install xp after windows 7 has been installed. Not the ideal way, but I thought it worked. Used a boot manager program, and the 7 install disk to fix the startup, and it was working fine. Startup options show Windows 7 and xp. Went to boot into xp the other day and it just hangs at the blue welcome screen, in safe mode as well. I don't want to go through the usual xp fixes, or should I. In this case, without windows 7 installed, I would probably boot the xp disk, go to the command prompt, and use the chkdsk /p or sfc /scannow option.

My question, before I attempt this (I probably will anyway), is will these affect the boot manager at all, or corrupt the windows 7 boot up?

or, does anyone have any suggestions to how I can get the game (Your Shape, by Ubisoft) to run in 64-bit windows 7 (the game is fairly new and probably runs in 64-bit windows, just not with my hardware)
I've tried all kinds of compatibility mode settings, and no avail. The problem that happens, is the screen flickers. kinda like the refresh rate is wrong, but it's a laptop, and I don't think there's much of a choice to change it. it's set for 60hz. Same as the desktop settings. I've tried other games, and have had no problems. Like I said, when I had the 32-bit RC version of windows 7, it was fine. Changing the graphics card is out of the question.

Thanks in advance for anything you can think of.

 

My first suggestion would be to boot into windows 7 and run easyBCD http://neosmart.net/dl.php?id=1

Rewrite the windows 7 bootloader and make sure that XP is in the list, then it should be OK.

If not post back and we will pursue other options.