My Dad may need a new PC for his home business (just himself so a decent home PC will be fine) but it MUST be reliable.

All I can think for reliable/good support is Dell. Years ago I used to by a number of Dells (my mum has one) and they've all been well built and never have problems with them. Are there any others that have good reputation.

He already has a monitor so that may not be required.

What's the best value reliable desktop out there?