So all scans have so far came back negative (not actually tried TDSSKiller yet) but annoyingly I actually haven't seen another advert, I have no idea what kind of adware shows one pop-up then sits quietly for two weeks. If I knew I would complement them on their design, I guess this isn't as intrusive as I said.
I couldn't find any obscure or unrecognised programs, it's a pretty new pc build with few installed programs which is why I was concerned it may have been a Microsoft thing, glad it isn't though.

Thanks for the help though guys! I'm afraid I have no idea where to go from here so I guess I'll just leave it alone for now.