Text (or multiple files/folders) selection seldom works on Inspiron 3543

When I try to select text or multiple files/folders using the touchpad, the selection quits as soon as I release the left click button, and sometimes even opens up the last file (or all files) on which I drew the selection (in case of text, it simply just aborts selection).

This happens for first 7-10 tries, then for next 4-5 tries selection starts working perfectly, then again it becomes buggy after these 4-5 perfect runs. And the cycle just repeats itself.

BUT, there is no problem whatsoever if I use an external mouse. Selection works perfectly.

I am running genuine Windows 7 Ultimate 64-bit.

The dell technical support representative tried several things/options, then finally said your laptop is compatible only with Windows 7 Professional and Windows 8/8.1

Everybody knows Ultimate is a version higher than Professional, i.e., Ultimate includes all features of Professional.

Funny thing is, even the driver is exactly the same for all windows versions :  http://www.dell.com/support/home/in/en/indhs1/product-support/product/inspiron-15-3543-laptop/drivers?rvps=y

http://www.dell.com/support/home/in/en/indhs1/Drivers/DriversDetails?driverId=C3XGM

I would like your opinion over this.

P.S.- Touchpad was already replaced with a new one on my laptop, still the issue isn't resolved. The previous one also had the same problem. (reasons for replacement were some others too, including this reason as well, this was among the insignificant ones).