"automatic private address"

This is a serious problem.
My uncles computer keeps using an automatic private IP address and it wont renew.
I have tried all the basic stuff and some other technical tricks but nothing seems to work.
But he has real windows xp sp1 wit an integrated SiS900 network card and its wired cable internet.
help plz!

Is having an automatic private IP address causing problems with his comp? If so what kind of problems. How long ago did this start happening? Were there any updates / installs made to the comp prior to this happening?

you know what I'm not sure anymore if that's the problem anymore.....
i believe it started happening 5 months ago or less but he didn't realize the prob cause he had no Internet turned on.
i have trying stuff out 4 a few weeks now.
So the problem is it wont connect to the Internet and wont allow the ip address to renew.
And about the updates and installs idk its way to far back to tell
but if u have any ideas or questions let me know plz!