Does Windows XP Pro have a 3GB limit on RAM ?

I just wasted a nice amount on buying a rig of 4GB ram installed. I forgot to check whether it will be used by XP or not. Now it cannot return the same also. I checked many articles about that 4GB usb switch. But nothing was found. I just founded a link on web that talk about 4 GB RAM Tuning feature. I am not able to understand much of this. Also I am doubtful about using the options that are provided in the same. Hope some geek can read and post a much easy solution.

A description of the 4 GB RAM Tuning feature and the Physical Address Extension parameter

There is one issue with 64Bit system. Many users here had emphasised on purchasing a 64bit system for those who expect to have more performance. But 64-bit system are the one which lacks a better compatibility support. You cannot easily find drivers for them. Also whatever application, game you are using you will have to buy the 64bit version of the same. I had assembled many systems and normally I receive complain from users who simply are irritated with the driver issue.

Well that is right. The drivers things are bit buggy in Windows 64bit. They are basically recommended for server which needs more basic software support only. I have a Lenovo system me. It is 32-bit and I had contacted Lenovo to provide me upgrade for more ram. They said that the ram is limited and there is no way to go for more upgrades here. My dad has a desktop which has 4Gb ram and Vista installed. The memory management looks to be poor for 32bit system. The system still uses the page file as additional memory which simply adds more to the count.

There can be to ways by which you can assume to make 4GB work. First as said by others the x64 operating system. In this kind of systems the Intel PAE allows memory mapping above 4GB. Second you need a hardware which is PAE aware. So that it can be able to address RAM above 4GB. Now this looks like a bit difficult to find but there are chances to get the same. Both 32-bit OS of Vista and XP has the same issue while Linux kernel is facing this from start.

A description of the 4 GB RAM Tuning feature and the Physical Address Extension parameter

The answer looks a bit informative. There are still very rare chances to have 4GB or higher ram on 32bit system. That limits the performance of basic computers. While if you are using a 1GB gpu in your system with 3GB ram then you can assume to have 4GB RAM in the system. Where 1GB is dedicated to video memory only and it will not be utilized for any other purpose.