Well the PC has slowed down to a dead crawl, and nothing is working as well as it should (Explorer crashes when you try and do almost anything on the digital camera).
So the wonderful solution is to RE-INSTALL!!! I really hate doing it as I am always so paranoid that something will go wrong and I will loose all of the data.
Speaking of that, it was lucky that Andy suggested that I check the backup CD's as the contents of disk #4 would not read at all!
Formatted the CD and did the backup again - it takes around 2 hours as the CDRW's that I am using can write at a max of 4x. In the end everything can now be read so will start the re-installation this evening.
Now I can see why a DVD writer would be oh so useful!