When to ask for help

I was facing some problem (Technical) and was unable to solve it. I was trying various approaches, but all seemed to go in vain..I showed the piece of configuration file to my collegue(Debendra Tripathy). The moment I showed the file to him, he observed that a couple of lines were commented. When we rectified it, the problem was solved . Thanks Debendra!!!!
Just for the stats :
Total time taken for my friend to solve it - 10 seconds.
Total time I wasted on the silly problem - more than a week.

So that bring to mind an important aspect. After how much trying should we ask for help. Ofcourse it would not be wise to aks for help even before you try yourself (because everyone would be busy with their own work). But there should be some parameter by which we could figure out when to ask for help. The approach I have used till now is, Try as many solutions as you can think of. But still if you are not able to solve the problem, then ask for help. (Though this may not be a good approach if you are involved in mission critical tasks.)

Do let me know if you can think of any parameters to find out when to ask for help?