Yes, less than 4GB is available on x32bit systems as area51reopened wrote ^^^, but if u have more, it will not show in Windows, but u could use the excess RAM as a RAM disc. RAM disc can take advantage of unused RAM. That is, if u have more than u can use on the x32bit system.
BTW, RAM disc will shame any SSD in transfer speed!
U can encode music, video, zip kind files or use it as a cache and have speeds u have never seen before : )
RAMDisk @ http://www.filehippo.com/download_ramdisk/