Use of External Hard Drives and Flash USB Drives

I can not open to view my files on my USB external hard drives (80GB and
larger) or my flash USB drives (1GB to 4 GB) from My Computer or from Windows
Explorer. I run Vista Home Premium on Inspiron 530. Vista recognizes and
assigns drive letters to the devices when attached but when I double click or
right click to open the files Explorer hangs up and eventually returns 'Not
Responding'. Windows shows the devices as 'working properly' and the drivers
as up to date. How do I get Windows Explorer to open these external drives
so I can view, copy, edit, and paste, etc.?