For help connecting a PC to a receiver or TV, you can try that HTPC forum, or the TV or Receiver forums, depending on what part seems to be giving the most trouble
It might be possible to connect the USB drive to your blu ray player which in turn you connect to your AV Receiver.
This depends on the USB drive, the format the movies are in and the blu ray player you have.
Of course if the drive is in your computer then connect the computer via HDMI to your AV Receiver and use something like Windows Media Player Classic to play the files, if doing that you might need to ensure the output range isn't clipping black levels.
I sometimes use a USB converter stick, i put a 64GB SDHC card into it and can view the files directly by plugging it into a USB port on the television, very useful if it's not a film and you don't care about multi channel audio for those particular programmes.