Hmm, I think I know what's the problem - you might need more RAM memory for your computer to run it smoothly, or perhaps more disk space needed? But photoshop does require some higher RAM memory, though
Continue to run CS1. I don't think it's a big difference between the two personally. I just upgraded to CS2 because thats the only 1 I could get a hold of but before that I was working with Photoshop 8 and thats all I needed. So continue to use CS1 and you can Delete CS2 or vice versa.