OfficeXP you can install with a proper CD Key, but you will need to activate it in order to be able to use it after 50 times running it.
For the English version there is a crack that can bypass this, so you should not worry too much on that (don't know where to get it, got myself an original version, thanks to M$ )
If you happen to have an original version and you want to activate it, you need not register (they want you to, but you are not obligated to do so). No personal information is sent to Microsoft during the activation process, only the hardware generated key with which Microsoft will generate the activation key.
As far as what I am told, no personal information is sent to Microsoft if you have OfficeXP installed, be it legal or illegal, all you have to do is bypass the activation procedure so you can use it without any problem after you have saved a document or run the program 50 times.