The chassis fan on my PC grumbles intermittently - on for a few seconds then off for a few seconds then back on again and it's driving me mad. It's still under warranty but it's back to base and I can't do without it for 3 weeks. Is there any way you can lubricate these things - WD40? Ideally I'd like to fix it or replace it with another fan, they seem so cheap but don't want to invalidate the warranty.
How about contacting the vendor and see if they would be willing to supply a new fan for you to fit yourself rather than returning the whole system to them for something so simple. Either that or ask them what would invalidate the warranty on the machine?