How can I see processes running in Windows 7?

In the windows command line you can use tasklist to list all running processes.

You can pipe the output of tasklist (as well as any other command line tool) using the "|" character. I almost always use tasklist in this manner.

The GUI version is called the Task Manager and there are a number of ways to access it.

What you want may be satisfied by Task Manager (Ctrl-Shift-Esc), but in case you (or others reading this) want more information, another option (not built into Windows but supported by Microsoft) is Process Explorer from the Microsoft SysInternals suite. It is way more useful if you want to do more with that list of processes and see more information. Very very useful to track down tricky system problems.

Process Explorer was developed by Mark Russinovich, author of the various Windows Internals editions and now a Technical Fellow at Microsoft. It has an active support forum.