Windows 7: Problem starting pc with dual boot XP-Windows 7

Oh no. Just decided to install Windows 7 on the second HD following all your directions. Luckily didn´t have problems booting XP on the other HD after setting partition as active.
However now I realized I installed Windows 7 without formatting the HD. I haven´t plugged the other HD back. Would you advise formatting and reinstalling?

So where did you install Windows 7 when you arrived at the drive selection screen in Step 7 of Clean Install Windows 7?

Or did you even bother following the steps in that tutoria provided because you were too bothered to try to understand how to get a perfect Clean Reinstall - Factory OEM Windows 7?

If you selected the correct partition where you wanted to install it then it doesn't matter if you formatted it or not, since the installer will do it by default anyway.

Post back a screenshot of your Disk Mgmt drive map and listings, using Snipping TOol.