Consumer law is on your side if Sony sold you a PC on the basis of it having something that it subsequently turned out not to have.
This would inevitably come under the 'description of goods' clause - in other words selling something that ultimately failed their sales promise.
If it was a shop assistant who told you that the PC had USB2 ports you might be on sticky ground as it would come down to his/her word against yours. However, if there is documentation supporting the claim - such as a manual or point of sale litrerature) that it was USB2 enabled you have a very strong case.
