If you have the system running with default settings, often Windows will do things like:
having Windows Media Player index all your media files so it can find them for its library
index your drives to speed up search
if networked the system may check remote files for changes so they can be downloaded for "offline mode" access
also if you have any programs that monitor folders for changes they can cause inefficiencies like Explorer opening every file on your system to see if it has been modified.
Usually the above will cause lots of hard drive running on. If your disk LED seems normal then they may not be the culprits.
I don't run a gadget bar so I'm not sure how much they use up resources. I run a lot of small hotkey programs but they are usually pretty light on memory requirements. For little utilities I download what I want or "roll my own" rather than using gadgets.
Look through all the running processes with something like http://technet.microsoft.com/en-us/s...rnals/bb896653
then search on them if you don't know what they're for. Some may be "user agent" apps that just keep checking if their main program has been updated on the web. A lot of that type of stuff will install if you let it. A good freebie that watches for that type of stuff is WinPatrol