XP Pro - i8042prt.sys ERROR - upgrade failed - I'm now stuck

Hi

A new retail version of XP Pro SP2 arrived this morning.

I opted for an Upgrade over XP Home.

I got past the enter Product Key - the system restarted.

A long white bar was on the bottom of the screen.

The upgrade stopped with this error;

i8042prt.sys is corrupt - SET UP FAILED.

Goggled i8042prt.sys relates to keyboard.

I changed my keyboard over - still got the same problem.

I have no idea what to do now.

Thank you.

Stephen