0 memory detected!?

[GreaseMonkey]

i installed zoo tycoon for my nease today and everything went as normal. when she came to play the game it pops up with an error message stating

"minimum memory required for this game is 256mb, detected on your system, o"    

this is impossible as i have 4GB and at any given time theres always 1GB or 2GB free?

i dont know but ive been getting a lot of strange things lately.

any help appreciated
thanks

[Ivan]

4gb = register overflow (either zero or -1 in 32 bit speak)

So 0 memory available is right...