Zoo Tycoon 2 does not work with Windows 7 (and from the research I've done, Vista as well) due to RAM issues. Following the steps below fixed my problem.Error Message: You need at least 256 MB of system memory to run Zoo Tycoon 2. How to activate rise of iron.
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(xxx MB detected).Problem Resolution:1. Open the start menu2. Type 'msconfig' and hit ENTER4. Look for the Boot tab (this should be the 2nd tab from the left)5. Click Advanced Options.6. Tick the box beside Maximum Memory and set the number to a high amount (I set mine to 4096)7. Reboot and run Zoo Tycoon 2 again.
Zoo Tycoon 2 RAM ErrorI don't think it's a RAM Error. I played Zoo Tycoon 2 with the Endangered Animals expansion pack in Windows 7 and it worked great. My system has 8 Gb of Ram and I'm running the Windows 7 64 bit RC. That being said, Zoo Tycoon 2 Complete will not run on my system & I get the same errors as you reported.
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The only difference between the two programs is the copy protection used. It is most definitely not a RAM error. Find the copy protection Complete uses and you'll find your problem.