Is it possible to get back my 12 bitcoins from 2010-11

So when i was 13yr old i bought 20 bitcoins and used 8, then i forgot all about it until few years ago, and now i cant find the website i used to buy it. It was greencargo or something.. i still got the same windows 98 pc with the same hard drive from when i bought it. I know the login info. But cant find anything else... Ive seen people done this before but dont know how. So i wonder if it is possible or a lost cause