Not sure if false positive but funny things happened when intalling AVAST

There is a small programme that you can use to find out what is taking up the space - see the following destructions

Please download and run Winstatdir

When the little pacmen have finished investigating the drive you will be presented with a visual image of your folders
Select the folder using the most space by clickin the little + sign alongside it
Locate the folder that is using the most space
If there is a + alongside that then click it to dig deeper
Highlight the offending folder and press Ctrl + C this will copy the path to your clipboard
Then right click the folder and select open
This will then open explorer to that folder… Do you recognise it ?

As for OTS a speciallist parsing tool is required, However, OTL does have a full tutorial here http://www.geekstogo.com/forum/topic/277391-otl-tutorial-how-to-use-oldtimer-listit/

Many thanks for the reply and help.

I hope it may be of help - I use it sometimes when I spring clean my system ;D