Well if it's just a backup for archiving purposes you could always try compressing the file with something like 7Zip or WinRAR and tell it to split the archives so that they're 100MB each. (Individual file size limit is 100MB on SkyDrive right? I haven't used SkyDrive yet.)
Or, you can try something like this:
How to Use SkyDrive’s 25 GB as a Mapped Drive for Easy Access - How-To Geek
You can create a folder in SkyDrive, then map it as a network drive on your computer, then just copy and paste.
Though I will say, 6GB is going to take quite a while to upload unless you have a speedy internet connection.