Re-installing windows 7 on different partition/prive?

have installed W7 64bit on separate partition (was H) on 2nd HDD (15mins)leaving XPPro on Drive C.
After install Win 7 has re assigned itself as drive C and drive C is now drive D (which didn't exist before(well - used by DVD). XP isn't shown as an available OS but have managed to see and use it using EasyBCD to add it to boot manager. On reboot however, once win7 or xp has been chosen, closing down and rebooting offer neither as an option with error
file \boot\BCD
status 0xc000000f
an error has occurred while trying to read the boot config data
Both systems seem to work fine but have to repair the 7 installation first. One thing I did do was assign Win 7 as a different computer name and I have read this might cause problem

Should I reinstall win 7? Any help gratefully appreciated

Perhaps change the drive letters back. Xp was installed in c: Now it's d: and trying to boot from c: !