|I would reccomend installing a good antivirus program.|
Unless you are going to be using lots of usb flash drives from different people or use the flash drive in lots of dodgy machines, you are more likely to get a virus online than via a flash drive.
Some antiviruses (Kapersky comes to mind) will ask you every time you plug in a flash drive if you want to scan it before use.
It does not have a password prompt however, and I am not aware of any software that does that (but there is most likely SOMETHING out there).
EDIT: I am not 100% sure what you are asking for...
If you are after something to prevent others from accessing data on your flash drives then something like truecrypt may be of more use.
The only disadvantage is that you will need the software on all computers that you plan to connect the flash drive to.
message edited by thomasad