my disc free space is diminishing itself, please help me!

kthouz

Hi! please help me!
I am having a real problem this days about my free space on my local disc C. Sometimes when i turn on my computer i find that the free space on my local disc has diminished itself without that i have saved anything on it before . This is very serious because there is at least 1GB that is decreased everyday. where is gone that space? does any one know?

To solve it, i try to erase some of my documents. There also is another trick that i use but it doesn't work always: i connect another USB external harddisk and the lost space is sometimes restored itself.
I have tried to defragment it but it doesn't cure it at all. I thought about the disk cleanup but it doesn't work neither.
So is this a virus or what...?
In case you need to know, my OS is windows vista premium.
Thank you in advence

Defennder

You might want to check your drive for errors. And of course a virus scan. I scan my drive regularly with an updated anti-virus regularly.