While shopping for Microsoft Windows XP Professional I've learned about the differences in two versions being offered.

One has the manufacturers part number or SKU number E85-02665 and the other is E85-02667. These are both English language but the version with #E85-02667 is meant for distribution in the UK and associated countries. The #E85-02665 is for the US and Canada.

These numbers are on a label on the box that the product comes in.

 I contacted Microsoft about the E85-02667 UK version and asked if this would work okay in my PC here in the US. They said it would work but that it has "significant program differences" than the E85-02665 US/CAN version. Also the support  office for the UK version is in the UK and the US/CAN version support office is in the US. 

These are both XP professional full versions. They are not OEM or upgrades. The E85-02665 retails for around $300 at the store. On eBay the E85-02667 UK is selling cheaper than the E85-02665 US/CAN version but be aware that sellers are not describing E85-02667 as a UK version.

I don't know of anyone using the UK version in there PC in the US but I didn't want to be a guinea pig and find out if it works okay without problems because of the programming differences between the two so I'm sticking with E85-02665,the US/CAN version.

Caveat Emptor - let the buyer beware.