Security researchers have identified performance problems with a recent wireless driver security update from Intel. Vulnerabilities in Centrino device drivers for Windows and Intel's PROSet management software prompted a security update three weeks ago.
The initial update weighed in at more than 100MB, though Intel did produce a
slimmed-down update soon after. The current driver release for the 2915ABG/2200BG wireless cards is 9.0.4.17.
From:
Intel Wi-Fi update ate my CPU cycles | The Register
Intel Wi-Fi update ate my CPU cycles 
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