Steam won't start after crash

[The B]

Recently I've started having problems with Steam. It will randomly crash during a gaming session, and then any attempts to start it up again will not work. Sometimes it doesn't even need to crash, it just won't go at all.

It will show the "verifying installation" window for a few seconds, if at all, and then vanish. If I try to start a game up from the desktop, it will do the same thing.

So far, I've tried:

Restarting (obviously)
Running in aeroplane mode
Searching for steam.exe in task manager (steam bootstrapper seems to come up for a few seconds before it closes)
Antivirus scan
Deleting a variety of recommended files in the installation folder, eventually the entire thing apart from the launcher
Reinstalling (worked for about five hours of game time)
Running as administrator (worked once, but later in another session it crashed and the same problem remains)

My specs:
Lenovo Ideapad Z510
Windows 8.1
Core i5
4GB RAM
Nvidia GForce (don't have the exact number to hand, will update if required)

Thanks in advance!

 

[The B]

Apologies if anyone was typing up a response, I seemed to have fixed it - at least temporarily.

The solution was to download the steam installer and run it (as an administrator), but not uninstall steam first. This seems to have worked and the programme runs. I will post again if the problem resurfaces.

Edit: it does create some problems with the games, in which case you will need to validate the integrity of the files in Steam.

 

[The B]

It was indeed a temporary fix - the same thing happened. Steam support are being generally useless. Does anyone know what is causing this?