Damn, you ninja'd me again mta, but I spotted your post this time. ![:)]()
I was thinking along the same lines. 150gb is big as mine is only 350mb. I'm wondering if there may be some program which isn't cleaning up after itself, such as video/audio converting software using that location for it's temporary converting process and associated data, and then leaving it behind.
I've had software like that and a folder can get big real quick if you do a lot of stuff and aren't aware of what is being left behind.
That WizTree is good. Very fast and better than the one I was gonna suggest.
Another thing worth mentioning is that not all software cleans up properly after itself when uninstalled. Usually appdata and local appdata folders are left behind but sometimes even Program Files (XP name) stuff is left behind, which is why dedicated "Install Tracker" and "Uninstaller" programs exist.
A good free Install Tracker is ZSoft Uninstaller available here ...
http://www.zsoft.dk/index/software_details/4
A good Uninstaller is Revo Uninstaller. The free version is available here ...
http://downloads.tomsguide.com/Uninstaller-Revo-Pro,0301-10196.html
Care needs to be taken with Revo, but it does have a variety of Uninstall levels which means you can stay safe if you aren't too experienced.
And please call back for advice if you need any.
![:)]()
EDIT: Just discovered that Revo Free isn't compatible with 64bit systems if that's what the OP has.
2012 topic worth a read on Unistallers/Trackers ...
https://forum.piriform.com/?showtopic=36381