diagnostic hardware + software

[pc_user_nb]

Hi-

I am looking for some advice on the best diagnostic tools that we can get for our pcs.

I have symantec products and some freeware- but I really need to be able to run complete diagnostics on the pcs so we can see what the hardware + system troubles are.

Is there one product that is clearly the best?
I have seen info on micro 2000 but it seems hard to purchase.

Any suggestions would be greatly appreciated.

Thanks.