I'm using hp dv 2700 (chocolate brown machine). It's specs are:
120 GB hdd
2 GB Ram
1.67 core 2 duo processor
I have observed this a few days back. But I suspect that this has been happening for a month; because, a month ago my system used to hang up (so, it's safe to say that it has been happening for over a month). What I did was that I removed some of the installed programmes (by entering from safeMode), tried to run a complete scan from bootup (by avast freeedition). Moreover, I installed a couple of programmes known as wise disk cleaner and wise registry cleaner. Both of them proved to be a bounty and released a lot of my disk space. Besides, I also disabled the backup files that are created in vista in order to save my diskSpace.
After doing all this, I installed oracle 10g and connected it to jDeveloper and besides, I also installed visual studio 2008.
In a nutshell, these are the programs that i've recently deleted from my machine
Macromedia flash 8
Music and movies (cleaned approx 15 gb (however it was not in C drive))
these are the programs that i've recently installed
wise DiskCleaner
wise RegistryCleaner
Oracle 10g database
Microsoft visual studio 2008