I have an HP media center PC that is 5 years old. It has an Intel Quad core, 2.4Ghz processor and 3G ram. Recently it has been making a clicking noise and twice I lost the signal to the monitor.

I don't have the skills to repair it myself. Any opinions repair or replace?

Two common reasons for clicking noises are a failing hard drive or something interfering with an internal fan. New mechanical drives are currently approximately $70+ depending on capacity plus whatever labor costs at your local computer repair shop. However, given the age of the machine and your skillset, if cost is no object, I suggest replace, but odds are it could be repaired for significantly less than the cost of a new machine.

I'm in a similar situation. I have a 5+ year old HP media center PC and yesterday when I turned it on nothing happened. No sound, no lights, nothing. While waiting for my local repair shop to open I was thinking about whether to have it fixed or replace it with a new one. I decided that the new machines may be a bit faster than what I have now but otherwise there isn't a huge advantage for me to get a new one and spend all that $$$ if the cost of repairs isn't huge.

It ended up needing a new power supply. It cost $60 and was fixed in 15 minutes.

Whatever you decide to do, I suggest that you back up your data immediately so that you don't get stuck without it. I had backed up a few weeks ago and spent some of my waiting time yesterday patting myself on the back for it. :)