I'm starting to sell computers and i was wondering if i can copy my windows xp pro oem cd to distribute with computers that i have purchased a windows xp pro oem certificate of authenticity.

Possibly, however check with either Microsoft and/or the vendor you purchase the COA's from, i.e., Marrisel/Ingram/Techdata etc...

As a system builder myself, working for a company, we are obliged to sell the OEM copy of XP Home/Pro with each system we sell that the user purchases an OS with. Since each copy of has it's own CD-KEY sticker we then place this on each box after resealing the pre-install.