7-Zip

7-Zip 4.57 is an free compression program which is better than other programs like Winrar and Winzip.

7-zip is integrated in the Windows Explorer, therefore you can use the right button on yout mouse to archive or extract your data. Also you can check your compressed files on errors.

The advantage is that 7-zip is freeware, instead of Winzip, and it offers the biggest possible compression of all compression software programs. (and therefore the smallest files)