Recently when I plugged in my thumbdrive, the folder showed nothing at all. Went into the properties and the system still managed to display the amount of space used and available. Tried scanning the folder with anti-virus software and it managed to detect files inside the thumbdrive.

May I know what happened to it? How do I get back my files?

If the space used shows that you files should still be there, then you should just have to take ownership of the files to be able to see them again. Please link below for how to do this:

How to take ownership of a file or folder in Windows XP

Please post back this does not work.

I'm using Vista. Does this work?

Yes the instructions are essentially the same. If you have problems try the following:

In Windows Explorer right click the USB drive > Click Properties.

Select the Security tab > Click Edit > Click Add > In the Enter obeject names to select box - type your username > Click OK
Highlight your username in the Permissions screen and tick Full Control - Allow.

This does not change ownership but should give you access to the files.

Please post back if you still can't access your files.

I don't seem to have the Security tab when I right-click Properties:

Try the doing the following:

Click Start > All Programs > Accessories > Right click Command Prompt - Select Run as Administrator.

at the prompt type the following:

icacls d:\ /t /grant everyone:c

or

icacls d:\* /setowner username /t

Substitute the h for the drive letter of your usb pen drive and if you use method two substitute username for your usename.

Post back if this doesn't work.