There are too many malwares and pests that masquerade under that title.
Here's Grif's note that I might try but first let's hear more about this system.
Then Please Try This.. - CNET Spyware, viruses, & security Forums
<span class="st"><span class="f"> Windows cannot access the specified device path or file. You may not have appropriate permissions this is the error message...I am locked out of my own pc... I tried opening shortcuts , click icons, open programs and get the error message. When I go to internet and put in search..I get any number of paid sponsor ads.. I cannot access my control panel or any other programs... I had AVG and foolishly let it expire but I tried to download a paid version from cnet..the error message came up again. I cannot acces my Windows XP Security system. Thanks in advance.