U could try upgrading the ram, but if u dont want to do that u can put the setting in the options menu of the game to as low as it will go so that it will run faster. Make sure the game is the only thing running on your computer, if u have something like a anti-viruse program or something else that is running in the background that isnt completely necessary, u should shut it off before playing a game. Make sure u have the newest graphics drivers and the newest version of direct x. Download all the windows updates.
Omega drivers run faster than regular drivers.
http://www.omegadrivers.net/
You should make sure your computer is almost double the minimum requirements for the game too, if your computer is just the minimum requirements the game will run slowly.
If you can still hear the music and move the mouse but just the game is frozen you should try control+alt+delete or alt-f4 before just turning off your computer by pressing the power button.
Press control alt delete and look at the performance thing and see the cpu usage and stuff, under processes u can see what programs use how much memory.
If u have an intel processor use the intel application accelerator, i never used this because i have an amd processor.
I read a book along time ago called
Hacking Windows Xp and it had a section on increasing system performance, i dont remember too much from it but maybe u should read that to learn how to increase your computers performance. I mostly did the things in that book that made my computer more secure, made my internet faster, and made my computer look cooler, i didnt really care about making my computer faster because it is already fast enough.