What eats up computer's memory?  

I dont know the exactly but i do think that Cookies,History,OR there must be files in recycle bin. to delete this all things you can use C-Cleaner.
Hopes so it will work.

Vista consumes lot of RAM for its own operations ,and any third party software like firefox etc take its own share of memory.

I would recommend either to upgrade the RAM to use WinXp with same amount of RAM.

Vista requires lot of memory to perform its basic operations.
Any third party application installed on it will again take its own share of memory.

I would suggest either you upgrade your RAm if you wish to continue with Vista or install WinXP on your current hardware.

Hi Vidasandi!

Vista needs at least 2Gig to run effectivley. programs, games, utilities use up RAM (memory). if you want to use less, then run one program at a time. if you upgrade your memory like others have suggested, it should sort the problem out.

Hi friend!Vista consumes a lot of memory.If you find that your drive is unnecessarily used up,just check the page file allocation.And also try to release some memory from the recycle bin.I hope you will get some unused memory.Thank You

Definitely upgrade your RAM, it's pretty cheap these days.

Also, for stuff like cache cleaning and the like, I'd recommend installing something like this: http://www.ccleaner.com

temp files and restoration cache.. use pscanner to clear it all.. clear also your windows prefetch weekly or once a month.. :)

What I'd recommend you do if you don't want to upgrade your ram, nor downgrade to XP, is to disable Aero, by changing your theme to Windows (right click on desktop --> Personalization --> Theme --> Choose from the dropdown 'Windows Classic'). Also, turn off side bar (in tray, right click sidebar logo and click 'properties', and unselect 'Start SideBar when Windows starts', click okay, then right click again and select 'Exit'). Finally, if you have spare USBs, plug them in, go to 'Computer', right click on your usb, choose 'properties', go to 'ReadyBoost' Tab, and select use this device.
This should speed up your computer, and reduce the cache on your RAM...

Cheers...

You can use any Memory Optimizer tool to keep free your memory. There are many inactive icon on system tray which are not used still they eats your RAM. better u stop those useless program from system tray it will release some memory .

There are many programs for doing that. You can download some by simply searching Google, with keywords "reduce cache freeware" or something similar to that.

You can also remove unneeded applications from control panel. In case you do not know how to do that, you can take help of Google again. Keywords: "uninstall programs vista".

You can press ctrl+alt+delete, then click on process manager, then end a few processes that you can recognize, and that you do not require, such as the one of the anti virus, that you are using, in case you are not logged on, or in case you feel you haven't done anything that should case a virus outbreak.