XP "activation" issue

[SHRED]

Working on my friend's computer:

Replaced PSU, motherboard, CPU, and RAM...hooked up existing HD and DVD.
Would boot only to Welcome screen and then it would auto-restart.
Didn't have his OEM genuine XP disc with me so popped in mine instead.
Booted to disc.
Ran a repair mode.
It installed and asked it for Key so I used mine.
It loaded and I was relieved that his info and files were still intact.
It performed a lot of updates.

Problem is now the activation window won't come up. The webpage telling me it is not a valid copy does but no activation ability.

Questions:

First off...should I have NOT used my copy due to the fact I an running it also on my computer?
Should I get his copy and re- run "Repair" again so that I can put in his Key when promted?
Why is the Activation window not coming up when I go to Start>All Programs>Accessories>System Tools>Activate Windows?
Is this possibly an Internet Explorer issue?

thanks

[CK_John]

1. At this point save what needs to be saved. Redo install with proper key and take note of MS phone

Your friends key may be on the PC box, but you need it and the disk(there are several versions of XP disk, Oems may have built in key).

But... both keys may have been flagged and a call to MS 800 number may be needed. Like talking to the police don't volunteer any info just answer there questions and say thank you.

[SHRED]

2. thanks for the advice but...

UPDATE:

Ran a little freeware called: XPPID.exe
Got it over at Softpedia.
This allowed me to change the product key code to the correct one.
It validated just fine.
All is well.
;)