Recently M/S has started to use a small active x app to CHECK to see if your USING Genuine M/S software .......
We have all seen it when we go to the Windows update page or go to D/L ANTISPYWARE BETA ......... In any event ........in the last few days perhaps a week .....the check has been adjusted to pickup OEM versions of  Windows XP ......... and you will get the result of the scan reporting .....VALIDATION FAILURE ......... Invalid product Key ....    I spent 3 hours on the phone yesterday finding out what is going on ........... the result is that M/S is aware of the PROBLEM and are working on it and expect to have it corrected by the end of the week.
This will only happen with OEM versions of XP ...or so I was told ......   the good news is there is a work around for it ........

dl65  Thanks for the tip DL!

I am using XP pro and had to validate earlier this week to get the updates. It let me have them but I was given a warning that said something like "the product key used is ASSOCIATED with a major manufacturer and the hardware found in your system does not match the expected configuration. This will not cause you any problems right now but may in the future" or something along those lines.
I have upgraded the computer so I'm not suprised the  hardware config is not what they wanted to see. My question is this, does making a hardware change invalidate the license agreement on an oem version?gliss......If I understand the way it works is ...it looks at your systems hardware and if it see major changes ...you may get that response ....... When Win XP pro was first activated ...for example the system may have had say one HD and a cd ROM ........ but since then you have added hardware ...say another hard drive and say a burner ....... But the big issue might be if you have changed the MOBO .......now it lools like a totally differant machine and probably has a new machine name ......... If that was the case , you would probably have to contact Microsoft and explain that you had changed the mobo .....Remember that the license allows you install on one machine.......
As it was explained to me by Microsoft this current issue only applies to Xp Home OEM .....but it may well be that it applies to Pro as well .

Hope this answers your question ........but if you have the time ,why not go to the horses mouth .......Microsoft and ask them the same question .

dl65  Much thanks DL 65! Actually when I changed the ethernet card it made me reactivate. I had to call microsoft and explain that I had made a hardware change and they where very nice and cooperative about it. So I just didn't see why they now indicate that this could be a problem in the future. If I get the time I'll give them a call.