If "My Computer" takes a really long time to open on your computer, you are most likely experiencing a well-known issue where Windows hangs while trying to search for network folders and printers before displaying anything to you.
This problem is easily solved, and most of you are probably familiar with the fix already, but we'll go through it anyway.
Open up Folder Options from the Tools menu in Windows Explorer, and then choose the View tab.
Uncheck the box for "Automatically search for network folders and printers", and close the dialog.
The changes should be immediate, and your problem should be gone.