a longshot, but one to check before spending money.
When you first start the computer you should see a message that says something like "press f2 to enter setup" or maybe delete, hit the key it says at the time and it should take you into the BIOS of the computer, have a hunt round on the pages in there to see if the USB ports are disabled or switched off.
Don't see it so often these days but older computers often the default setting in the BIOS is for the USB to be off and as you say the computer hadn't been used for a couple of weeeks if the BIOS battery is starting to die it may have reset the BIOS to default..
Oh and the computer clock will be wrong too if that is the case.