XP?
try using safe mode to resolve your problem, I think you can uninstall photoshop from there ?
just hit the power button on your case and then hit F8 repeatably until a black screen shows up with a bunch of options move down the with arrow key and select "Safe Mode" and hit enter
windows will boot up with a black background and words "safe mode" in each corner, you can access the internet or other networking connections in this mode but you may be able to uninstall Photoshop and see if that helps your cause