My C drive is 74.5 GB . after installing windows 7 ultimate with some softwares not much, but it's full it's showing red colour. How to get free space in my c drive, i tried many options.
75GB is NOT a lot of memory, mind depending on what you do. You can buy hard drives relatively cheap nowadays that will give you a ton more space to deal with. But if that's not your route. I recommend removing unnecessary files to clear up some space. (Large files, little .txt documents aren't going to cut it)
I would advise you to run disk cleanup as well as delete the temporary files. Also, it may be a good idea to adjust your System Restore settings. You can decrease the amount of storage allocated for that.
Check these out: http://www.howtogeek.com/125923/7-ways-to-free-up-hard-disk-space-on-windows/