Hi Katy,
To compress or uncompress files, please refer to:
For Windows XP:
How to create and use compressed (zipped) folders in Windows XP
http://support.microsoft.com/kb/306531
For Windows 7:
Compress and uncompress files (zip files)
http://windows.microsoft.com/en-US/windows7/Compress-and-uncompress-files-zip-files
Considering this question is about Windows and we have specific forums for Windows clients, it is recommended that you go there fore help:
Windows client forums
http://social.technet.microsoft.com/Forums/en/category/w7itpro,windowsvistaitpro,windowsxpitpro/
Thank you for your understanding and cooperation.
Hope this helps.
Nicholas Li - MSFT
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