Compression help, please read.
 

So i just renderred my file as an avi and it's 25 gb...... How do i make it smaller? This has never happened before.

Use .wmv instead and lower the quality to around 80% and it should be fine.
Otherwise if you want to use .avi get the divx codec and render is at divx instead. It should lower the quality some but greatly reduce the size.