Was my hard drive hijacked?

[dirtguru]

Not sure what happened? Early last week I noticed my one terrabite primary HDD had only 10gb of free space. Normally it shows aproximately 400gb free space.
Ran Malwarebytes and Disk Clean Up, sys logs etc showed nothing out of the ordinary. Computer performance did not seem to be affected. The only issue I could detect was the impossibly low amount of free space left on the C drive.
Life in general did not allow me to get around to attempting to figure out what the problem may be until today.
This afternoon I began by opening "my computer" and noticed my C drive free space had increased to 30gb without any action taken on my part? Closed and reopened my computer, free space now at 120gb?
Close and reopen again, 260gb free space? At this point I went online and began searching for what my problem may or may not be.
Currently my C drive has returned to normal, on its own? I have no idea how this may have happened?
Defrag and Malewarebytes are scheduled to run at 1:00AM Sundays and Wednesdays respectively after which my C drive still only showed 10 gb of free space.
Any ideas as to what I should look for or do so this doesn't happen again or is this normal?

 

[ICIT2LOL]

Hello and welcome dirtguru try this mate start at point 15 http://www.sevenforums.com/tutorials/220165-troubleshooting-steps-windows-7-a.html

there are these too

http://www.superantispyware.com/


http://www.bleepingcomputer.com/download/adwcleaner/
download form bleeping computer

Meant to add take all external stuff out first.

 

[dirtguru]

Gday and thank you for your quick response. About to run system file check.
Checked some forums regarding Superantispyware and most reported numerous problems which of course often means there are many more folks running problem free. Do you use Superantispyware and if so how would you rate?

Thanks again, will post what I find.

 

[ICIT2LOL]

Gday and thank you for your quick response. About to run system file check.
Checked some forums regarding Superantispyware and most reported numerous problems which of course often means there are many more folks running problem free. Do you use Superantispyware and if so how would you rate?

Thanks again, will post what I find.

Well basically I find it keeps the ad clutter at bay for the most part.