I am having the same problem as the author in this thread http://www.experts-exchange.com/OS/Microsoft_Operating_Systems/Windows/XP/Q_24192838.html#notices
and I am not computer savvy. My USB devices are acknowledged, but when I try to open them I get "Access denied." In the expert's accepted solution, he states it's probably the Device Wall Control as the culprit. I don't know what that is, how to uninstall the software and reinstall it. I'm sure my current installation has been corrupted by a virus. My computer was redirected to a malicious site and after that I ran Malwarebytes. It showed one virus, which I removed and the next day, the first time trying to access the USB device after doing so, is when the access was denied. It worked prior to that, yet I have no clue why it wont work. I tried updating drivers, but it wont let me.
Can you help? I'm on XP Pro.