Error Coming While Installing Vista Transformation 8.1

I'm not a tech expert but I'd like to advise you against installing VTP on that system! 640MB of RAM just isn't enough to work well with that eye candy. It WILL slow down your computer a lot! I had 256+128 MB of RAM earlier and it took 10 mins for the desktop to become useful after a startup! Even Microsoft recommends 1GB of RAM at the very least to enable Aero Interface.

As for that problem, the installer might be corrupt like everything on Digit DVDs nowadays(if you picked it up from Digit DVDs). If not, I regret that I can't help you.

try doing it in safe mood,may or may not work but i suggest you get pack vista inspirate ultimate and turn off rocket dock

Is it the actual VTP 8, coz I never faced issues with it.
Get it from www.windowsxlive.net/
should not be a problem installing it on SP2.