This has been discussed numerous times in the past. It's the nature of the beast I'm afraid. You've got a major PC problem, you get advice on here, it works, and suddenley your so excited about having your expensive PC working again that you set about doing all the things you haven't been able to do whilst its been broken, updates, check emails, etc etc.
You go to bed happy and just totally forget to thank the people that helped. I've been guilty of it in the past, I don't mean to be rude, you just forget sometimes.