Dell keeps hanging up on me, want fix or return laptop

I purchase a Dell Studio 1558 two and half months ago.
I've had problems with it since the original purchase.
I called them as soon as I had the first problem which was on day 3.
They insisted on troubleshooting the problem.
I was fine with that.
I've spent literally 40 hours on hold and troubleshooting the issue.
They've removed, installed, and reinstalled drivers.
They've had me reinstall the OS, Windows 7.
Finally they said I had a bad harddrive.
They sent a refurbished harddrive and I'm still having the same issues.
I want to return the laptop at this point because it is defective.

Now they're saying it must be a software issue.
I haven't downloaded anything on the new harddrive! It was probelmatic from the original installation.
They are saying I must pay to have them check the software.
??? I keep asking to speak to someone regarding returning the defective laptop for a replacement or a refund.
After being on hold and transferred numerous times I keep getting "disconnected" once I finally get to the returns department.

I've been writing down all of the Dell reps emplyee name's and employee id numbers.
What is my next step? I'm at a loss.
I don't know what to do.