Trying to run hardware test on 07 iMac with noisy fan (and BT keyboard...)

Hello

I have an 07 iMac with a noisy fan- I've tried vacuuming out dust from the back but want to avoid taking it apart if possible...

I read online I should run the hardware test, but since I am running Mavericks the Apple support advice is to run the original OS X install disc and restart (holding down D or Option+D)...

Long story short I got a replacement disc from Apple (I'd lost the original) but the iMac ejects it when I restart following the process above... could it be my bluetooth keyboard? Hopefully not since I no longer have the original hardwired one... or does anyone have any other ideas for either how to get to the hardware test... or fix the fan (without a third party app just stopping it)

Thanks!

 

Anyone?