no, emu’s cant break your computer whatsoever and they are legal. Basically, its a virutal machine running the PS2’s BIOS and code. If you just download one off a website, its going to be hard to configure and setup right, also not all PS2 titles are able to be played currently… But for the few select ones, you would have to download the emu, find the US version BIOS file…
Method A: (This is also the LEGAL way) In order for you to actually run the emu with the game you need to load the PS2’s BIOS to the emu…the only problem is the only way you can obtain them is though the network port on your PS2, you have to connect to your PS2 though your PC via ethernet, then extract the BIOS from your PS2 and hopefully you wont brick it…aka dead ps2
Method B: (This is the ILLEGAL way) Searching around the interwebs until you find a website and or a link to get someone else’s…
And on top of that you have to have a pretty powerful PC to run it too, and i think from your other question you said you had vista… and vista probably won’t run it correctly because you know…vista doesn’t like ANYTHING cool or fun…
Also, ROM’s are the illegal part of it, if you get the bios from your PS2 and load it with your PS2 game, its completly legal… but not if the ROM’s were downloaded or you got it from you friends… GL HF Cheers