I have a very crappy power supply and am worried about having power issues if i put my new hard drive in as a second hard drive. I recently put in a new graphics card that is a power hog compared to my old one (128 mb 9800 pro compared to a geforce 4 mx 420). My computer is really starting to get sluggish (havent reformatted in 2 years). So, instead of putting my second hard drive in and backing up data and reformatting, I was wondering if this was possible: could I just replace my old hard drive (120 gb) with my new hard drive (200 gb), boot from the windows xp cd, partition it and install windows xp? If I wanted to go back to my other windows for some reason, could i switch out the hard drives again and boot from that windows?