thank you, I will check that link out. Seems like I am always working old computers!! They never have the same problem!! 
Yep - in a way, they never do. Altho I will say things are much better in the last 6 to 8 years. CD drives made in 2002 would often not read CD's written on a drive made 6 months later.
I agree that a run of diagnostics is a good idea. Imo, it's not that likely to turn anything up, but hardware issues do happen. Sometimes you can have a running OS installation working with a bad memory spot, and not really notice an issue - the occasional crash gets blamed on something else. Ditto hard drives. Take an extra day to run thorough tests, it can't hurt.
As to the partitions, I assume your 3 partitions are "/", "/home", and swap. You might want more than 4G for "/", for instance, if you install OO, and other office type software. This year I've had better luck with 5.5G. I do run a lot of stuff on my office boxes tho. Earlier this year I did have some very similar experiences to yours, trying to install linux systems, and running out of partition space. Quiet, but very complete, failure.
For RAM, even though you say the box has "enough", it would be helpful for you to tell us how much RAM it has.
If the CD's have worked on other installations, that's good. When you say the install fails when installing software, can we assume it is getting the software packages online, and NOT from the CD? If you are just using the CD as a source, then it could be a compatability issue, but I think that unlikely, since you are getting this far along in the process. If you aren't using the CD as a source at the time of failure, the partition size would be the first thing I looked at.