Your 7 gig partition is your recovery one (i know that it doesnt take 70 gigabytes just to make a recovery partition). Go to mycomputer, and you should see the different partitions on your computer, and double click the unknown partition and see if there is anything important, (if is loosng its ntfs file structure then it cant even be read by windows, is it FAT, or FAT32? If it isnt then maybe it could be a linux partition that you might have installed? if it isnt any of those then you can just delete it, because if it was important and windows cant read it but windows stil works [therefore not important because windows works without it], therefore rendering that partition useless).
-I hope u understood the logic behind the paragraph above.