if i want to install windows 7, will my old files be deleted?

can any of you recomend me good and free online files storage cause i wanna use it to store my files as back up.

Better to create 2 partition with Hard Disc.
Disc C: and Disc D:

Put all your important files to D: partition. Move or Copy all what you want from C: to D: ( My Documents is part of C: , soo copy that too )

Now install Windows 7 on C:
All your files on 2nd partition will be safe..