RAM usage stays high after using and exiting programs

Hello everyone,

I just registered a new account here at THGF, but I have been using these forums for a very long time. I always got my answers through searches, but this time I couldn't get my answer.

After using Camtasia, some adobe products like Photoshop, Audition, Dreamweaver and Windows Live Writer my RAM usage stays very high.

My computer spec:

Intel Core 2 Quad Q9550
8GB Kingston HyperX 1066
System HD 200 GB WD SATA
3 X 1TB Seagate HD SATA
Asus P5-Q Mobo
Sapphire HD5850 Graphic Card
Windows 7 64bit

Running programs:
uTorrent
mIRC
Internet Download Manager
MSN Messenger
Winamp Agent
Eset NOD32 64 bit
ATI CCC

When I boot into Windows 7 my RAM usage is below 25% but after using those programs and exiting them, my RAM usage stays at 58%. My computer isn't slowing down or anything like that, I'm jut wondering why this is happening and is there a way for me to lower the RAM usage after exiting those programs without doing a reboot.

Thanks in advance.