Handset flash needed I think?? - Help Please.

[Northern Soul man]

I've got a CG5 mount with a Nexstar + HC, it was bought new in 2013 - not had to worry about up dating the HC yet - but I think its now time to re - load the firmware back on - set up tonight and wanted to do a quick solar system align on the Moon - but tried several times to do this - it gets to the Solar System align screen the I press to continue, the screen then freezes with "one moment ..." and hangs here, I've tried a factory reset a few times, but just gets to the same place and hangs there forever - so I've got the grey serial to the base of the HC - so I need a usb adaptor - wonder if any of you can point me to a relevant adaptor cable I need - I think serial to usb - but not done this before - so not sure - I think I've heard that certain adaptors don't work and the HC is not recognised through the CFM software - so any advice really welcome.  Thanks in advance.

Paul.