Hi Sue
1/
Snow leopard is only for Intel based Macs – thats any Mac Pro Tower or any iMac without a “G” in its title.
The differance with Snow Leopard is that it is written only in Intel Code and runs simpler and faster than OS X 10.5 (and earlier versions)
because they have both codes (Intel and PPC) so you could run either at the time of changeover of code.
So to sum up in your case.
If you are running a G5 or G4, Snow leopard will not “see it” and its time for a new Intel box – even the basic Mac Pro will do unless you are a heavy user (big Photoshop files or two hour DVD’s with lots of chapters.
Me, I like the look of the mew macpro with the 6cores…
2/
Media 100 downloads
Go to M100 site – downloads – down to the 10.6 -click on it and install it – the opening window has a info/code section
It is a trial version, within 14 days enter your code you have been sent, and the 14day bit is erased, its your’s forever!!
Hope that helps
Bruce
Oh yes, click on the apple logo top left and it will tell you the type of Mac you have.