I have Adobe CS2 installed on my machine but I now need to use Adobe Flash Pro as well.
I'm hoping to buy Adobe Flash Pro (either CS3 or 4 version) as a separate product but need to know whether it will work on my machine or would I need to update the whole of my Creative Suite to CS3 or CS4?
Having CS2 on your machine should not have any influence on your ability to install/use Flash CS3 or CS4. They should not conflict with each other. The only problem you might find is that your system is not capable of supporting CS3 or CS4. To determine that you need to check your system against the minimum system requirements. If you aren't able to determine that, you can always try to download and install the trial version of CS4.