Why did my laptop stop working?

A year ago I installed Steam on my laptop and a lot of games on it. Over the next week or so, the laptop became slower and slower (it couldn't play video or games smoothly and kept freezing, and even the movements of the mouse cursor were very jumpy). Then my computer wouldn't boot up at all, and although the store managed to retrieve most of my files, I had to buy a new hard drive. I always assumed this happened because I had so much on my laptop (it also carried quite a lot of music), but I was told recently that no amount of memory can damage a computer. I've also never heard of downloading Steam damaging a laptop. My aintivirus software was also out of date, so do you think it was a virus that affected my computer and that the timing of the download was coincidental, was it actually because I had too much memory, or did it die for some other reason? My laptop is fine now, but I daren't install any games on it.

Model - Advent Roma 3000, Processor - Intel Pentium T4300, Memory - 4096MB DDR2 RAM, Hard Drive - 500GB