We use Laptops with HDMI very often for display calibration, and rarely have any issues.
To be honest, I can't remember the last time we had an issue...
Some simple checks to follow can be found here: http://www.lightillusion.com/data_tv_levels.html
There are a couple of simple way to check is levels are basically correct.
Clipping is obvious with test frames, as shown in the link above.
And with a decent probe check for no black lift.
With the TV on, but with no input signal measure the black level.
The send zero black to the TV from the source and re-measure.
There will likely be 'some; small variation, but not much, if all is correct.
If there is a mismatch the variation will be a lot greater.
And yes, you do need to make sure all Windows colour management is off.
Hope this helps.