Installing SP3 for WindowsXP

I downloaded SP3, but run into problems when installing. I did successfully
install on my laptop (Windows Professional) but the problems occur on my
desktop (Home version). Halfway down the installation process I get various
application errors (UpdDlg.exe, rundll32.exe, MyUrsSrv4.7.0.566 to name
three, all with the naration:"instruction at 0x5a00d0e0 referenced memory at
0xe5e66544. memory could not be read".
I hope someone could tell me how to overcome this. Thanks Herman