Running Out Of RAM.. With 9% CPU Usage - Why?

I have attached two screenshots from my task manager taken approximately at the same time, when my computer was running very sluggishly.

I have a

3.0 GHz Intel processor
1.5GB RAM
x1950 PRO ATI graphics card
Running Windows XP with Vista theme!

Where has all the memory gone to? Why is my computer using so much virtual memory? You can see that there are only 62 processes (which may be a lot but still!) and the highest one uses 81K; the rest are insignificant - I have ordered them by Mem Usage.

So why is only 5k memory available?
You can see that the CPU usage is all minimal at this stage yet the memory has run out.

http://img516.imageshack.us/img516/8332/taskuc1.jpg

I know a thing or two about computers but I can't explain this! What's the problem?

http://img184.imageshack.us/img184/33/cpuru3.jpg

 

But with 62 processes running that does NOT help it shoud be around 30.

So those screen are just after a reboot you have done nothing ?

 

They're not after a reboot. I have been running the computer for 3-4 hours and I was just watching a film in Windows Media Player but the screenshots were taken about 10 minutes after I closed WMP down and was only running those processes.

Just after closing down the media player the computer was almost completely frozen, couldn't do anything so I just left it. When I returned, it was recuperating slowly but with those stats in the screenshot.
Yeah it may have been a bit overused but this still shouldn't be happening to a computer with those specs and that's why I thought I'd post here to ask for opinions.

It's not the first time it happens; I've restarted the computer now and it's all fine at the moment but I'm looking to do something to prevent that sort of thing happening in the future.

 

@ Crystak
Yes , that seems to be too many processes running at one time. How many do you have running at start-up? If you are not using all those apps at the same time, the processes do not need to be running.
The last thing shown in your screen shot is using 81,484 KB. What is it and does it need to be running?
Trim down your start-up and see how your RAM behaves after that.

@ Creativeballance
I don't know if this is the same Vista Transformation Pack but have a look:
http://www.majorgeeks.com/download.php?det=4924

 

I'd say get rid of that vista transformation pack, and roll back your system restore to before you installed the thing.