XP re-installation issues

Hi,

I searched a lot for this issue ... didnt find a solution ...

Anyways .... when i choose the upgrade option to reinstall ... i enter my 25 digit code ...the files start copying (i think the core files .... windows hasnt restarted at this point btw) ... and i get a file missing error here ...mostly some .sys file which changes every time i restart and try to reinstall again.

Then i try the fresh install option .... i enter my 25 digit code ..... the files start copying and properly end up copying ... begins to restart but i stop it coz there's a lot of data on my comp that i cant backup or lose.

So basically i can do a fresh install but not a reinstall

Any solutions?

Thanks in advance