Windows 7, Xp 32 bit reads only 3.25 GB RAM ?

It is true that 32 bit OS can only read upto 3.25 GB RAM, if you are having 4 GB ram only 3.25 GB is utilized and rest is simply dumped into waste. Even this difference is found in Windows 7 32 bit,

you can simply check the system properties, we can find that only3.25(4GB) RAM is read.

Only 64 bit version  can read full memory, we can test it by installing a 64 bit OS version you can definitely find that  full 4GB RAM is noticed.

Comparing 64 bit with 32 bit , 64 bit runs definitely fast. Those who are having 8 GB or more than that we can find that a 64 bit OS is installed.

Hopefully this post can be useful for you.