Help Reinstalled Vista - Swapped data on partitions?

Well this morning I logged onto my Windows Vista Ultimate x64 computer and noticed all kinds of problems. Most notably my computer slowing down to a crawl and then failing to load applications forcing me to either wait a long time to surf the internet for solutions or hard reset. From reasearching the web I found taht others had the particular problems I was having and have gone through extensive reasearch for weeks and through many forums to find no solutions. As I've only gotten my computer 30 days ago I know that this is unlikely to be hardware related and decided to simply reinstall the OS.

Well I just reinstalled Vista on the C: drive where it was installed previously, I never would have thought it would of made a backup of my C: drive and swapped all the data to my D: drive which Is my main drive I use for gaming etc. Now that Vista has damned me I was wondering how I could get back my old apps and games onto my D: drive that are now on my C: drive thanks to Vista, and be able to operate. I believe I need the registry to recognize the games, how could I copy the registry or would the registry bug out?

Was their a possible way around this?

In short: The data on my D: drive is in a windows.old folder in my C: root and the old C: drive data is in my D: drive