Hi Roz
A five year life isn't particularly over optimistic for a hard disk, particularly one in a home PC which probably hasn't been worked that hard. Of course one should always backup key data 
Although you say there is an error message, you don't say what the actual error is that leads you to suspect the hard drive. I assume we are talking about a desktop PC (which is probably a 3.5" IDE drive at that vintage) as opposed to a laptop.
The easiest thing to do would be to get it out of the machine and connect it via USB to another PC to see if the contents are readable. You would need an external caddy for this though these are pretty cheap or you may find someone who has one. Something like this
http://www.storagedepot.co.uk/Hard-Drive...4/p88.aspx
If the disk can't be read in that way, it is probably uneconomic to consider any form of recovery. Feel free to send me a private message if you have questions. I am not particularly a hardware specialist but I have worked in IT long enough not to be scared to poke inside the box a little bit.