Every time i try to open unity 3d, it closes immediatly. Please Help.

How can i solve this problem? Unity 3d is located in my Program Files(x86). Im running on Windows Vista. And my Firewall is off. Any suggestions?

If the problem is project related (and not license/firewall related), you can hold down the alt key while Unity is loading to bring up the project selection window instead of auto-loading your last project.

the thing i did was disable the firewall >prefrences>secuirty> firwall = off

then it worked just fine i hope this works for you.

You can only install Unity twice on two machines. If you have installed it on more your third install will do this if you had Pro installed before. If not I would try re-installing after cleanly removing if you are using the free version. If that doesn't work contact Unity because it seems it is bailing on the license check.

I had the very same thing happen to me with Vista x64. I tried everything with out any success and had to format my Windows in the end (but don't do that without exhausting every avenue)... but you could try these things, they have worked for some people:

  1. Disable UAC.
  2. Allow Unity.exe in DEP settings.

(just google the above and it'll explain how to do both those... really easy).

I hope that fixes you problem.