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File bdfdll.sys is located in a subfolder of "C:\Program Files".
Known file sizes on Windows XP are 8,704 bytes (61% of all occurrence), 7,808 bytes. However, some malware camouflage themselves as bdfdll.sys, particularly if they are located in c:\windows or c:\windows\system32 folder.So I suggest you run a full scan.If that doesn't work , you may try doing a system retore to bring the computer back in time when the issue is not yet present. For Windows XP:
1. Click Start, point to All Programs, point to Accessories, point to System Tools, and then click System Restore.
2. On the Welcome to System Restore page, click to select the Restore my computer to an earlier time option, and then click Next.
3. On the Select a Restore Point page, click the most recent system restore point in the On this list, click a restore point list, and then click Next.
Note A System Restore message may appear that lists configuration changes that System Restore will make. Click OK.
4. On the Confirm Restore Point Selection page, click Next. System Restore restores the previous Windows XP configuration, and then restarts the computer.
5. Log on to the computer as an Administrator. Then click OK on the System Restore Restoration Complete page.
For Vista or 7:
1. From within Windows, you can just type restore into the Start menu search box, and you'll immediately see System Restore at the top of the start menu:
2. Then please follow the on-screen instructions.
Hope this helps.