The differences between Acceptance Testing and System Testing?

Are they the same? Or, System Testing is performed by the testers and/or programmers while the Acceptance Testing involves with the customer?

Take a look at what each type of test is describing. An acceptance test is testing if the system you are testing is acceptable to the end users - i.e. the clients. Usually this involves a general test to make sure that the program is acceptable. There may still be some bugs in the sysyem (for example, some localization bugs, or a more serious bug if the user does something extraordinary), but as long as these are not a hinderance to the general use of the program, the program can be delivered (think of Microsoft - if they took the time to fix every single bug they and the clients came up with, we'd all still be working with Windows 95).

A system test, by comparison, is a test of the system the program runs on. So an acceptance test might say that the program runs wonderfully on Windows 95; but if the program crashes when you try running it on Windows 7, and the majority of the clients are running Windows 7, you need to change your system test.

This is, of course, a very general answer, but the key also is that both tests should involve the testers and customers. Testing that involves just a tester or a developer (such as Unit Testing), is something that should be done WAY before you get to the stage of Acceptance or System testing.