>>>I have run into this before, but haven't really researched it. I am horrible about keeping my Windows XP CD's and I usually keep them as ISO's and burn them to a CD when needed. Sometime a particular key doesn't work with a CD so I try the next CD and it works. Are there different versions or something? I don't think it is the OEM version. I have the regular key on the sticker on the side of the case and it says it's an invalid key.
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>>Yeah, from what I've encountered over the years there are different keys for:
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>>- full version vs. upgrade
>>- full packaged product vs. OEM (and probably vs MSDN, academic etc.)
>>- XP w/o SP (i.e. "SP0"), SP1 and SP2 (and the soon-to-be-released SP3)
>
>OEM license keys have OEM in them, don't they? This doesn't - it's a regular key. It's not an upgrade either. It's an IBM desktop and we bought it with XP installed on it, so maybe it IS an OEM license.
>
>We also bought it before SP2, so that can't be it.

Could also be a Corporate version of XP.