Linux Mint Forums

You can run it in Virtualbox under Windows?
This indicates that there is a problem with your graphics card as Virtualbox uses a virtual card
Try compatibility mode - there's a good chance it works
Post back and tell us how you manage - if it still is a failure tell us about your hardware as detailed as you can
You see dell optiplex 320 does not say much - can be different hardware in the same model, but I know old optiplex can have problems

I recently installed Mint 5 GNOME on an OptiPlex GX150 (P3-1.3GHz with 512MB RAM) and everything worked fine. You may wish to check the amount of RAM you have. Using the Live CD with 256 MB is syrup-slow, but once installed, has no problems. Some OptiPlexes might be troublesome, but the one I worked with was easy. I just wanted to share with you that it can be done. Good luck, and have fun.