I installed Ubuntu 12.04 LTS on Windows 7( on C: disk) through wubi (Windows Ubuntu installer). Windows7 has crashed but Ubuntu stills works.
My question is if I install Ubuntu from a removable disk that I create on current system (Ubuntu) with MAke STartup DIsk, on which disk (C: (currently installed on) or D: (my personal files)) will it install Ubuntu permanently? I don't want it remove my personal files (about 700 Gb) on D: disk, I must be sure about it will overwritten onto C: (Windows files and current Ubuntu located).
Thanks already.

If you want to make sure that it writes to the first partition (you may have noticed tha Linux does not use the C:/D: notation) you have to specify it manually. The best option is to start from the CD you made in Live mode (not install mode), then start GParted and remove your Windows partition. Be careful not to remove your data partition (your Windows partition should be much smaller than 700GB, I would guess). After that start the installer and when it comes to partitioning tell the installer to use the free space.

Having said that, installing an OS and changing partitions is a system critical task. You should make a backup of your valuable data before that. In fact, you should always have a backup of your valuable data, otherwise it can't be valuable for you.