Everything on my computer constantly crashing?

For the past few weeks all the games and web browsers on my computer have been constantly crashing, and the Adobe Flash Plugin, but the Adobe Flash Plugin has been constantly crashing for many months. I use Firefox, and it's been crashing around ten times a day. So a few weeks ago when everything started crashing, I went to an MMORPG other than the one I usually play, and it started crashing a ton too. And, League of Legends has been crashing occasionally (though only one time has it been during a game) for the past few weeks also. This computer is I think less than a year old. It's Windows 7, Lenovo. As a matter of fact as I was typing this Firefox crashed yet again, and I had to retype the whole thing:/ This computer has Norton Antivirus and I've run scans several times to no avail. What should I do?

The RAM is faulty. Look around, but first try reinstalling the apps in case it was a different problem.

I think either the hard drive is dying or the RAM is faulty (likely the former). Do a full scan with SeaTools for DOS and see if the hard drive is ok. Then do a full RAM scan with Memtest86+.