Seriously. I've told you this. You need a new power supply plain and simple. Problem is that case has a weird for factor and getting a replacement power supply won't be easy since almost all power supplies for sale are standard ATX and your computer case won't fit those.
Also you need a low profile card. Unless you found a low profile 750 TI (I looked and couldn't find any for sale) then it obviously won't fit. Also judging by looking at your case you won't be able to fit any kind of card that is two slots wide.
It sucks but you really shouldn't spend any money on that machine. You can only fit a low profile and single slot video card, which severely limits any upgrade you could get and also you need a new PSU regardless of what you get, which is going to be hard to find and expensive since it's not a standard size. If you want, measure the dimensions of the power supply and see what you come up with.