Dell laptop randomly locking

laptop randomly shutting down

I have a gateway laptop w/ amd turion 64x2 processors,windows vista. I use to be able to play games all day, do 10 things at once and my laptop was fine. All of a sudden i have ran into the problem of my laptop randomly shutting down. At first it was just shutting down when i was playing video games [games that doesn't even have the greatest of graphics and that i played ever since i had laptop which has been for about 2 years]; ide say i would be able to play about 5-20 min and randomly would shut down. Then i stopped playing video games on this and now just download music and playing music and if i am downloading music and playing music and converting music it will shut down on me. Seems to keep getting worse and worse, like today i was just browsing the internet it it shutdown on me. I did get a blue screen the other day as well, first time it has happened to me on this laptop. If anyone could tell me what this could be i would greatly appreciate it.

Another note: If i unplug my laptop from the recharger i can usually play until the battery is dead, but it will make my computer real laggy and choppy so its not even worth to do when playing games.