I have created a GUI on Python 2.7.11 that consists of a main page along with page 1 and page 2 that are linked through buttons on main page. Converted main page to a python exe file using PyInstaller and there were no errors in the conversion. main page.exe appeared in the dist folder but on clicking it, a DOS screen flashed and the main page did not open nor persist on the screen. 
Being a beginner, I am not sure about how to proceed further. Please help.
If you've got a line like root.mainloop() at the end (with root standing for your main Tk window) to make sure the event loop runs, then you'll need to debug your code. Try running a small segment of the code at a time to see if all goes well, and see where it is that all doesn't go well; then examine the offending part closely to find the error, maybe running some lines of code in the interpreter from the command line to see what (if any) error messages you get.
On the other hand, if you don't have a line like root.mainloop() at the end, that could produce the error you saw. Being a Python beginner myself, and having learned to program in Tcl where the Tk event loop runs automatically, I've seen that error a few times myself. :o(
Tkinter exe file - DOS screen flashes but GUI does not persist