i built my computer about 4 months ago, has worked fine on all games i have played, it reached around 40 fps on GTA 4 all settings maxed out, on a 22 inch screen.
AMD Phenom X4 email@example.com (stock)
4GB DDR3 Ripjaws
Realtek ALC889A (intergrated sound card)
ATI Radeon HD5850 (stock clocks)
Windows 7 Home Prem x64
i loaded up prototype and restarted the computer and pulled up prototype, set all of teh settings to max and started to play, at the start, there was no sound and after listening carfully i found that the dialog was going past so quickly that you couldnt hear it. then after skipping though the start cut seen i started the playing of the game. again no sound except for small squeeks. then after that i got to the first concumation. i started it and then computer lagged so badly that i couldnt tell what was going on. then i got to the gentech cut seen but still the sound was in squeeks and the cut scene lagged so badly i could tell what was happening. i have tryed lowing the graphics and fiddling with the in game sound config but nothing has worked. also the graphics all though being maxed out looked terrible, there was no definition, when the blackwatch soldier called in a strick team it looked like he was talking into a green, grey, black blur that was i think his vest
Don't torrent games in the future. They are prone to having problems. Also console games adapted to PC generally suck. And prototype is no exception. Don't bother with it anyway, it's just a cookie-cutter sandbox game. I found it felt kind of old and run-of-the-mill. I played into about 10-30 minutes of it and was done. I was uninterested and bored really fast.
This sound issue is a known problem with Protoype in general on realtek chips(and others); pirated or not. You have to set your system to lower sample rate since the sound system in protoype was useless and doesn't adapt to the system it's used on.
The graphics system as well was also pretty poor in terms of AA and filtering. Make sure your graphic driver software has mipmap on the highest setting.