If you're going to change the virtual memory, one hint: THE START VALUE AND END VALUE MUST BE THE SAME. If they're not, the PC calculates everytime the virtual memory is used the start and end value, and that takes a lot of CPU ressources.
I have a value of: 3072 and 1GB physical RAM, though 1536 is enough.
@Kidwild: Nothing will happen, you just have then 2GB less on your HDD.