Hard drive space

Hi all this is my first post so hellllooooo.
My pc is running really slow again which is quite a common thing with this one and usually happens when the windows hard drive gets nearly full so for the last few years i have been transferring the data from there to the other internal 250hd or the external hd but the problem i have now is that it is a 250gb hd with 60gb being in the user folder which is the data i know of pics vids etc but when i highlight all the contents of the 250gb folder and click properties it only comes back with around 100gb being used so where is the other 150gb? Obviously the 100gb is 60gb of my stuff in the user folder and then the other 40gb for windows and all the other stuff on there but all my hd's are now full so if i could free the other 150gb up somehow then this would tide me over till i can either buy yet another external hd or a new pc.

Thanks

Thanks for the replies, i have just started a scan with the first one so i will take a look at the other one after.
While that is scanning I have found over 50gb in the appdata/local folder, how do i go about clearing this please? The first pic with strange folder names in total is only 11mb but all the other folders in the second pic are holding quite a lot of data, can i just delete the folders i dont mind losing the programme data from as the only ones i do not want to lose data from are the Garmin and Mozzilla or is it not as simple as that?

Well these are the results which may as well be encrypted to me i will have to look closer later but for now i just one question please, it states the drive being only 134gb when it is 250gb so how come that is?