My little brother needs a ethernet connection for his (aging) PC. I've seen USB-Ethernet adaptors which would be ideal (no need for him to open the box and fit an expansion card) but they are all USB 2.0 and his PC has just plain old original USB ports. Will this cause a problem?
Way back when IBM designed the original PC, it was always intended that ordinary users would be able to upgrade it with no hassle - that's why the power supply is a sealed unit (the highest voltage you will encounter inside even if you leave it switched on, is 12 volts).
As Ethel says "it's a doddle and takes all of five minutes. By far the best way to go, and cheap."