Hi, I trialed Mint 6 and liked compiz fusion... I have a Dell Pentium 4, 512 mb RAM Laptop, it goes well. I want to ask if I should install Mint 6 or 7, will it have the drivers?

I like 7 for the way I can chose it's space used, so I can run XP as well.

Dual booting if that is what you mean ?
Every distro gives you the change to dual boot , assuming that you're
hard drive is big enough
Most distros do have a Live CD .
If it works on you're system for essential parts it is likely that it also works when it is installed.
Benefit of a LIVE CD you can try it without installing
Beware when installing not to use the whole drive

Hi again and could you tell me with Mint 6, how I make sure I don't over write XP?

And can I choose the amount of disk space Mint takes, as it tries in Mint 6 to take a huge bite, all the free space?

First if win Xp is already running sometimes on you're hard disk defrag the XP partition first.
Second making a backup is always recommended just in case
Third shrink you're windows partition using windows or geparted
Geparted is a live CD.
Every distro I know of has a expert or customize partitioning.
Use this option to decide where to install linux.
You also should decide where to install GRUB.
As I am a linux user I always said in MBR
But you also can decide to install GRUB in the root partition of linux and
use bootini to start linux , but do not ask me how to use bootini to start
linux