Virtual Memory in windows xp! How much maximum and minimum to allocate?

I have been trying to speed up my windows xp .
I figured out that defining a particular figure to windows virtual memory, it can increase performance.

under system properties> advanced>peformance> advance I see virtual memory minimum as 1000 MB and maximum as 2000 MB .
I have 512 mb RAM in my system.
How much should I set ?

Virtual memory is the amount of memory other than the RAM which computer is supposed to use when it run out of RAM.
It is true if you give pre-defined size then it is better than system managed. If your RAM is 512 MB then you can assign minimum as 1000MB ie. around double of RAM and maximum 1500 Mb..
Though its better to have both equal ie. 1500 MB.. I prefer.

thanks

[p.s] I normally tend to go with original configuration - bid afraid of going in for advanced options.