Most file extractors will not use the full amount of free space on a hard drive, especially if it is the system drive. They will check free space and subtract some arbitrary amount, or percentage, that they will always leave free. If the remaining amount is sufficient they'll extract. Otherwise they'll pop an error.
They will also include the amount required for installation in the calculation. During the installation process you need space for both the extracted files and the full installation.
I just tried to take a look at my 2011.zip file to see what the uncompressed size would be and I get an error that the zip file can't be opened. Checked the backup drive and it's buggered, too. So I hope I don't need to reinstall.