Hi,
I heard that it is doable, because even if the GPU is soldered to the mother board, there are techniques to remelt the solder to replace the GPU. But as it is like a brain surgery, it shall be done under extreme attention, right tools, right monitoring and expert judgement. Such as you should use laser thermometers to monitor the temperature not to burn the motherboard while melting the solder. You have to be careful because there might be neighbor solders which might be melted too.
So to sum up, this procedure is highly risky, and no one takes that risk to proceed this upgrade. Plus i have heard people who burned their motherboard while trying to do that. Even one computer guy told me that, even if it is a success the GPU might got into problems within two years of usage as it will have defects in the procedure. So that's why people say 99% you can't change it. Which is sad, and i'm pissed off too.
In my case i have the same problem and i'm still searching for solution. I have a dell latitude 14 rugged extreme 7404 with i5 and an integrated GPU HD 4400 i guess. So in the owners manual i saw that there are instruction about how to replace the GPU ! Please check it from this link.
http/www.dell.com/support/manuals/au/en/audhs1/Topic/latitude-7404-laptop/Lat14_7404_OM-v1/en-us/GUID-9CCD6D90-C1D1-427F-9E77-D4F83F3AD2B6
Click the pdf button to get the manual. Search for GPU, then you will see.
I really wonder that if i can really replace my GPU with GT 720m ? I said Gt 720m because this laptop model has already an option to be bought with GT 720m, so i think that it should be compatible somehow. Further more i wonder if all these assumptions are right why not to use a GT 755m ? They seem similar ?
Any ideas on this voyage, please let me know. I'm just an architect so i really don't know much of these stuff. I really appreciate if anyone can confirm that this laptop can be upgraded or not.