computer boot frustration

Hi
I have recently re-installed windows 7. as I am going to give the computer away I want to remove the tb hard drive with my data on it.

when I boot without the tb HD I get system boot failure error. I have checked in the bios and the first boot drive is the one i installed windows on.

Once windows is running if I remove the power from the data drive windows behaves as normal. except it wont boot if restarted.

I don't want to reformat as I have spent a lot of time setting it up with programs my friend requires.

any help with this problem would be much appreciated as I have never even heardof such a problem.

Many thanks for reading