Hi Keast,

Quoting minimum and recommended hardware requirements from AVG Free Edition 2013 official user manual:
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Minimum hardware requirements for AVG Anti-Virus Free Edition 2013 are as follows:
Intel Pentium CPU 1.5 GHz or faster
1,2 GB of free hard drive space, for installation purposes
512 MB (Windows XP) / 1024 MB (Windows Vista, Windows 7)

Recommended hardware requirements for AVG Anti-Virus Free Edition 2013 are as follows:
Intel Pentium CPU 1.8 GHz or faster
1,5 GB of free hard drive space, for installation purposes
1024 MB of RAM memory

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So at least 1.5 GHz CPU Pentium compatible needs to be installed. You can of course try installing AVG on slower system, but I'd recommend installing only the necessary components (by using advanced installation and unticking some of the components which are not essential for you).

Please let us know if you need more information.