Hidden Bootkits found in Safe Search

Hello,

  Just recently, command prompt windows have been popping up on my computer, only to disappear seconds after they appeared. Due to both this and sheer curiosity, I decided to run AVG Free in safe mode. Amongst all of the other things scanned, I noted these in particular:

@Scan_BootSectorName|%name%=HIDDEN| Found Bootkit.61030040.F987090C is OK.
@Scan_BootSectorName|%name%=C:| Found Bootkit.61030040.F987090C is OK.

I realize that bootkits in general can be harmful to computers. However, could these be a false-positive? Outside of the command windows popping up, my computer has been running normally. Also, if it just so happens that these are not a FP, what steps should I take next to fix the issue at hand? I also have an external hard drive connected to my PC. What should I do to clean that as well?

                                                                                                                                                              Thank You,
                                                                                                                                                                  -Jack