I have an apple macbook pro i7 17" mid 2010 model 6,1. I need to do a hardware diagnostic on it, but don't have the DVD anymore, how can I do it? I need to to do a diagnostic test on my hardware, but don't have the diagnostic DVD anymore.  can I download it from some database?

it is a macbook pro 17" i7 2.66 Ghz
model 6,1  mid 2010
You should be able to run AHT from boot, by holding  D  at the chimes, assuming you're on something later than 10.7, Lion.

Ref: Apple KB - Using Apple Hardware Test