Currently Being ModeratedMay 6, 2012 9:43 AM (in response to AppleUserrr)
Within 1 year from the purchase date, limited warranty is in effect and it can be repaired
at Apple Store.
Within 15 days from the purchase date, you can either return or exchange.
Currently Being ModeratedMay 6, 2012 10:34 AM (in response to AppleUserrr)
if the buzz is continuous and gets more apparent as the Mac heats up, may be the cooling fan. The bearings on the motor can fail prematurely, especially in dusty environments. A fairly simple replacement wholly covered by the one-year warranty, as explained by dominic23.
To explore your warranty coverage and service options, get your serial number handy and see here: https://selfsolve.apple.com/GetWarranty.do