Buying a comp without an operating system?

[theordinaryboy]

hi there

i have my eye on a new comp from ebay, however, it does not come with an OS, i have also seen windows xp on ebay for a decent price and ill probably get it from there.

However, i am not the most computer minded person and am a bit nervous as to whether or not it will be difficult or complicated to install the OS.

Could someone reassure me that its easy or explain what i have to do please.

Cheers

p.s. is their anything else that i need to install apart from the OS.