Ok, may be I will be able to get some help with this. After not having much luck with my problem above, I decided to just start from the beginning with a clean install. I reformatted my drive, created two partitions of equal sizes, installed XP first, and then installed Vista. Everything seems to be working fine now. The only issue I have got is this:

1. When I boot into XP, I see two drives. XP seems to be on E: drive, and Vista on C: drive, as I can see files on E: drive when I click on it, but files etc on C: drive come up as hidden. When I try to install programs while in XP, the programs' installation folders automatically default to C: drive. I have to manually change this to E: drive every time.

2. When I boot into Vista, I see two drives - C: and D: drives, no E: drive. Vista seems to be on D: drive, and XP seems to be on C: drive. To make matter confusing, when I try to install a program in Vista, the program's folder defaults to C: drive. Also more confusing, is when I use a disc image creator like Macrium Reflect to make an image copy of my drives as back-ups, in Vista, it shows D: drive as active (with 12:22GB used), and C: drive as logical (with 26.03 GB used). In XP, it shows C: drive as active (with 12.22GB used), and E: drive as logical (with 25.63GB used).

My questions are:
1. For the purpose of backing up a disc image of my drives, which of the drives is actually XP to back up, and which is Vista, or which drives should I back-up as disc image for that matter?

2. When installing programs, do I need to change the default drive (C: drive), or does it not matter?

3. In XP, I can't actually seem to be able to navigate to desk top via windows explorer. For example, when I created a folder on my desk top in XP to use as default folder for downloads from Firefox. When I opened Firefox to set my default folder for downloads, I could not navigate to the desk top to select the download folder I have created.

Many thanks