Can anybody point me out to what version should I download, and process that would work with my Machine.

I wanna simply use a new hard Drive and install to fully boot Only *TIGER or LEOPARD* (which ever my Machine could be able to handle)

My Current Computer Details:

HP Desktop Media Center PC m7000
Intel Pentium(R) 4 CPU 3.00GHz
2 Internal Hard Drives - 200gb / 500gb
3gb Ram

I originally Do not know any details about the motherboard or anything internal extra of the machine, I think its only 32 bits (My machine is about 4 yrs old), I only know what I added(the extra internal 500gb hard drive & 2gb Ram chips). Original Operating System that came with is Windows XP MCE SP2.

I'm a Graphic Designer, currently my machine being old, its running Adobe CS4 Master Collection, pretty fast all good, thats to show my machine is still alive being 4 yrs old, and can handle one of the Newest biggest softwares around.

So thats all I know ... can Anybody help me out?
PLEASE EMAIL ME THE RECOMMENDATIONS & HELP: sendblink23@gmail.com
Since I'll receive it instantly directly through my phone the mail.

Anybody want to help me out?

BUMP, I need a right direction.. on what should I download