I found this solution that might help...
http://www.mcse.ms/message349955.html
It says to press shift-F10 to bring up task manager and terminate the unregmp2.exe process. Then it should finish. I haven't tried yet on mine. I have the same problem, It's too late for me tonight.
"rhonda" wrote:
> I was attempting to reinstall/repair WindowsXP when the
> following message appeared...Procedure entry point
> GetIUMS could not be located in the dynamic link
> library...
>
> Neither the "ok" option or the "X" will allow the
> installation/repair to continue. It is stuck on this
> page. PLEASE direct me from here.
>