XPS420 Drivers/ service pack 1

Hi this is my first post and im at my wits end trying to get my XPS420 up and running properly.

What happened is my hard-drive failed and i got myself a new one.. I used my original windows disk and drivers disk from dell ( that come with my pc)

I have installed windows must be now eight time plus....  but i cant seem to install service pack 1:emotion-9:

When the windows updates are going i get some failed one one occasion then the next time i restart the whole process i get diff windows update error.

I even tried to install SP 1 manually but my PC would not boot saying some files are missing, then we have to satrt over again.

I have searched  the net for a solution but this is my last port or call for help, after installing windows ( VISTA) i have installed the drivers from my Drivers and Utilities disk... i even when online to see if they have to be installed in a certain order, done all of this....even been on ms help page.. as far as i know i have tried everything there is to do so far.

Please any help would be greatly apprenticed.

Regards.