Unless you have a lot of text files (very few binaries) then you are not going to fit 640GB + 700GB (compressed) on to a 1TB drive. Your best bet is to back up your files (/home) and your configuration files (/etc) and anything else you cannot replace on your linux drive. Then reinstall linux after the format.
That being said. Don't take my word for it; try some archiving programs out.
Basic archiving programs commonly used are:
The 4 main compression types are:
- Zip (plain'ole Zip files)
- XZ-Utils (lzma)
If you want to compress a folder with tar and bzip2 then use:
tar -cfj my_archive_name.tar.bz2 /folder