Sounds bonkers but its this: 3.8 year old with cerebral palsy, very able mentally but arm movements are like an alcoholics shaky movements! Sits fine in front of a fabulous 21.5" Dell touch screen HD monitor and loves cbeebies games etc. Does not need to run playstation games etc.
Anyway today cheap and nasty old PC started smoking 
and is now binned.
I would like to replace it with a refurbished Desktop PC (tower only) that runs faster than the old compaq he had. Want to spend under £100 as it is simply to run this very expensive monitor at a speed faster than paint drying. I have gone completely blank regarding gigabytes, pentium processors etc..so what is the minimum I need? I've seen this...Pentium 4 HT 2.8GHz 1GB 80GB... Is that the kind of spec I need?