|All good rootkits load from the MBR. It is a part of the drive that does not get scanned by antivirus programs. Also the small unallocated part of your drive that is leftover windows installs can become a mountable partition by some tricky viruses.|
Okay, now you know that most computer my have some unsigned drivers installed, this is normal under most circumstances. You would only want to scan for unsigned drivers to find them, not remove them.
Once you find the unsigned drivers, you need to make sure that they are legitimate drivers and are the correct version, size, etc... this is what google is good for. If they check out, they should be left alone, they are not bad and are most likely functioning correctly. I think that TDSSkiller is finding these is what is leading to believe that your computer is infected.
Also for Note, this was copied from the kaspersky page:
"A bootkit is a type of malware that infects the Master Boot Record (MBR).
This infection method allows the malicious program to be executed before the operating system boots. As soon as BIOS (Basic Input Output System) selects the appropriate boot device (it can be a hard disk or a flash drive), the bootkit that resides in the MBR starts executing its code. Once the bootkit receives the control, it usually starts preparing itself (reads and decrypts its auxiliary files in its own file system that it has created somewhere in the unallocated disk space) and returns the control to the legitimate boot loader overseeing all stages of the boot process.
The main feature of a bootkit is that it cannot be detected by standard means of an operating system because all its components reside outside of the standard file systems.
Some types of bootkits hide even the fact that the MBR has been compromised by returning the legitimate copy of the MBR when an attempt to read it has been made.
A system infected with a bootkit can be cured with the TDSSKiller utility. "