There are two reasons why we need a lot of RAM today.
1. Because RAM can be accessed by CPU faster then Hard drive, modern Windows Operating Systems are designed to use this feature to run the programs flawlessly.
2. Modern softwares and games do requie a lot of rams. High resolutions with a lot of details are mostly dependent on Graphic Card RAM but we still do need a lot of physical rams too.
When you download a lot of videos all at once, you need a lot of RAMs. Famous browsers like Firefox do require a fair amount of RAMs. I was downloading 50 videos all at once but failed after 30% of download because of the shortage of physical RAMs.
Also, when you extract really large bunch of videos or any data, it eats up the RAM space too.
Loading 100s of Photos (to Edit) is the ultimate RAM eater too.
When you configure RamDisk, you should make sure that you have plenty of RAMs.
I have noticed that Windows XP still don't know how to deal with the memory leak.
If I can find the program to stop the memory leak, then I will post it here. I am 100% sure there are some.
Also, in order to keep the empty RAM space, you need to reduce your background service. turn of some unnecessary services and try to turn of the autorun of the softwares that you think it is not necessary. Eg. Anti Spyware. Scan whenever you like but don't keep them running all the time. As for the main antivirus software, you mustn't stop even it is not detecting any viruses.