Not sure but I suspect that your Nikon driver will not work with Windows 7. It would be worth checking the Nikon site to see if you can download a later driver. I don't think you can partition your had disk to run XP and 7 but you could install XP on an external drive. I found this on Google.
"You can install xp on a "virtual" drive (ie it is like a separate computer on you HD) -google for a program called Virtual Box and Install it. Its quite easy - just follow the prompts and accept the default options. once installed you can then install XP as a standalone operating system. When using this "drive" you dont have to shut XP down you simply save it in its present state (you can leave a file open) and next time you turn it on it will be just as you left it. I am using it very successfully, I have used PCs for yrs but recently change to a Macbook and then found I had programs that could not run on it, installing Virtual Box has given me the best of both worlds. Its worth a try - if it wont work you can just uninstall it - it takes about 10gb of disk space. "
I have not tried this solution so cannot vouch for it.