Steam simply will not start

My steam just wont start under any circumstances. I have tried literally EVERYTHING short of reformatting my comp.(which I'm trying to avoid). I have heard that virus scanners etc interfere, so I proceeded in uninstalling all of them, and still nothing. In fact now I can't get Mcfee back onto my comp. I have tried, reinstalling steam 7+ times and nothing. When I open task manager then click steam, steam.exe is their for 2 seconds top, then disappears. I went to steam support and they gave me some futile troublshooting tips, then I never heard from them again after that.

You guys have any ideas on what might be causing this?

Thanks,
Refund

 

The same thing seems to be happening to me with Gmod, a steam app.
Know what ya mean about steam support, it is useless

Sorry no ideas short of re-format
I will have a think

 

(Only if you have steam installed)

Well,try ctrl+alt+del

and go to processes ,and you should see "Steam.exe *32" .Well,end that process.Then click steam,and try to start it up,should work.