You were Wise buying a 250Gb..I bought the 128gb and with Micros updates its now half full. These updates soon fill the 128gb in a few months thanks to microrubbish..
Still, I am Happy with it, it's just the Magician that perplexes me.
It does seem odd. Me, being me, would be spending too much time trying to fathom out what's causing it !
I think I was wise to go for the 250gb non-pro. OK, I have to suffer "slow" write speeds (hardly slow, actually), but it's nice to not have to worry too much about how much space I`ve got left. I still think that the relatively small difference in price between the 128gb pro and the 250gb non-pro made the 250gb a fairly obvious choice. Yes, it's got cheap and unreliable memory, and just a 3 year warranty, and slow write speeds, but I`ve learned to live with those things.
Windows 7 with all of the updates should only take about 25gb of space, if that (my Windows folder is currently just under 18gb, but there may be other stuff hidden elsewhere). Yes, other "stuff" does build up and can soon fill a smaller drive. I`ve currently used 123gb of space, but that does include 3 full game installs, FreeOffice, a load of utilities and a lot of downloads that need to be deleted (I`ve been a bit lazy recently).
If you haven't already done it, it may well be worth you performing a "Disk Cleanup". If you have system restore enabled, you can get back quite a lot of space (but you'll only have the most recent restore point).