Compac cq50 110us has always run hot but now it overheats corre temp gadget reads temp at 205f then commences shut down vents are clear and a tech ie brother in law opened and cleaned system of all debris have cooling platform in place and small turbo fan blowing air under neath continuously still over heats

I find that when completely cleaning a laptop, I will remove the Heatsink/Cooling Tube combo.
Allows me to thoroughly clean in-between the fins, and around the fins, of the Heatsink.

Also allows me to THOROUGHLY clean, the bottom of the cooling tube's metal plates, that sit on the top of the Processor, and GPU.
(GPU = Graphics Processing Unit. Slang? Graphics chipset )

Also the top of the Processor, and top of the GPU.
Then fresh, new Thermal Paste is Properly applied, and the Heatsink/Cooling Tube combo reinstalled.

Thermal Paste dries up over time. When it does it looses it's thermal conductivity properties.
Due to the cost, and ease of replacing, it is just cheap insurance.

There may not be Thermal Paste used. Computer manufacturers also use a Thermal Pad.
A material soaked with Thermal Paste.

CANNOT be reused. Once the metal plate/s of the Cooling Tube squeeze down on the thermal pad, there is an imprint made.
Trying to reinstall the Cooling Tube, will not squeeze the thermal pad down any further than it was originally.
The same amount of pressure is used. A gap will result. In-between the surface of the thermal pad, and the metal plate of the Cooling Tube.
{Thermal Pad's are J-U-N-K. They loose their conductivity properties pretty quickly}

1) You were having a cooling problem in the beginning, and this IS one definite area to address, along with cleaning.

2) You are right there with full access, when thoroughly cleaning a laptop.
Access to the cooling system.

A) Did your tech i.e. brother-in-law address this issue?

B) If so what thermal paste was used, and what was the method of applying?
(Method of applying?
Yes. It matters. Especially if a compound like Artic Silver, or similar to, was used)

C) Cooling fan is rotating? Good. Now, what RPM is it spinning at?
Spinning too slow will cause overheating problems also.

Are you sure the Cooling Fan is not spinning intermittently?
Spins okay for a while, then slows down, or stops, then spins again.

D) Let's look at the Cooling Assembly, for the Compaq Presario CQ50 series of Notebook PC's,

Top View, palm rest (Top Cover Assembly ) removed,

http://www.insidemylaptop.com/remove-motherboard-from-compaq-presario-cq50-cq60-cq70-laptop/

Scroll down to Step 17.
To the upper left of the photo you will see the black Fan Assembly. (Most of)

{ Fan is inside a surrounding cage, or shroud. You can see some of the Fan's blades. The Fan and the Shroud, are the Fan Assembly}

Just disassembling down to this point, in order to clean, is Not enough.
You cannot thoroughly access the entire Heatsink. The motherboard must be removed in order to perform this.

You also cannot clean, and replace Thermal Paste.

Observe Steps 18 and 19.
Shows the motherboard being removed, and removed.
Same direction. Top facing up.

Observe Step 20
This shows the Bottom side of the Fan Assembly, and also shows the rest of the cooling system.

Fan Assembly to the top right. Coming down the right side of the Fan Assembly, and curving under, is the copper Cooling Tube. (The Cooling tube is a slightly flattened copper tube, sealed on both ends. It is filled with Nitrogen )

Coming along the Cooling Tube area under the Fan Assembly, is an aluminum small rectangular plate. This metal plate sits on the GPU,

http://en.wikipedia.org/wiki/GPU

Going further to the left, is the metal plate that sits on top of the Processor.
You see the four mounting screws for this metal plate, circled in red.

Step 21 shows the cooling assembly removed.
{The Cooling Fan Assembly, and the Heatsink/Cooling Tube Assembly, are two different assembly's.
Referring to both as the Cooling Fan Assembly, as in the article, is erroneous }

3) Heat from the top of the Processor, and graphics chipset (GPU) is absorbed through the Thermal Paste, and into the individual metal plate sitting on top of it.

The plates transfer the heat to the copper Cooling Tube. The heat is then transferred to the Heatsink, at the end of the Cooling Tube.

Air from the Fan Assembly goes through the fins, (And around the fins), of the Heatsink, and helps to carry heat away.

4) Thermal Paste
The top of a Processor, the top of a GPU, and the bottom surface of the metal plates which sit on them, is not perfectly smooth.

A magnified view would detail, 'Hills, Pitholes, and Valleys'.
When the two surfaces are mated together (Metal plate to Processor, metal plate to GPU), air pockets are created.

Created in-between the two surfaces.
Air is an Insulator. Not a Conductor.
Thermal Paste is an Excellent conductor of heat, and fills those imperfections. (Air pockets)

Tip:
When I state Thoroughly clean, for the top of the Processor, top of the GPU, and bottom of their matching metal plates, I mean THOROUGHLY.

For additional questions please post in a Comment.

Regards,
joecoolvette