Steam fails to load after boot up / Process cannot be killed / Hangs PC on 'Shutdown' Screen

[DreadedX]

The last three days have been horrible for me as a Steam user. I really don't understand what the hell is going on here. I have included in the title, the main problems as to what is happening. Everything was working fine on Friday. I booted my computer up on Saturday morning and clicked to open Steam (I don't have it start when Windows starts). Nothing happened. I clicked my shortcut again, still nothing. Checked the processes and found that Steam was actually in there however it would not let me 'End Process'. It simply would not close. So I had an open process of Steam.exe but no UI loaded, just nothing.
So I restarted my computer. It wouldn't go past the 'Shutting Down' screen. I had to manually reset. Turns out it was actually the Steam.exe that was stopping it from finishing the shutdown/reboot because whenever the Steam.exe is not running I have no problems. So aside from all this I have tried all the fixes I can find on the internet. That's the 'Clientregistry.blob' one and the deleting everything apart from Steam.exe and Steamapps folder and letting it update files. I have also ran as Administrator (even though I am the admin). After performing the latter it does then load Steam and reverts it to it's newly installed state. The problem then is that after I have shutdown the PC and booted back up, trying to open Steam again will not work. Back to square one. Rinse and repeat.
That is what I have had to do now since Saturday. If I power down my PC it seems to corrupt Steam and I don't understand why.
I have also tried reinstalling Steam from scratch. It was fine after me doing so yesterday. Then I log in this morning and Steam is no longer working...AGAIN.
So the only thing I can do is keep deleting the files and letting it perform an update by redownloading everything. Then I have to log in, put in another code that gets sent to my email, redo my Steam settings...I can't even be bothered to add Non-Steam games anymore because it just wipes them everytime.

Can anybody see a way out for me?! (before insanity finds a new home)

[blkmnky]

DreadedX, could you post your specs, with Windows Version?
Are you able to get into Steam right now?

[DreadedX]

Yes I can get into Steam right now but I bet that when I shutdown then boot up again, Steam will not be working.

I am using Windows 7 64bit. Intel i7 2700k @ 4ghz, Nvidia GTX480, 8GB RAM, and Steam is installed on a seperate SSD drive with nothing else.

This has never happened to me before, everything was working fine.

[blkmnky]

First I'd reccomend that you disable "Run when my computer starts" (okay I see u said it's off) in the Steam Settings -> Interface Tab. Then try opening Steam, Check for Steam Client Updates, logging off, and closing the program. Give it some time, (should not hang or take a long time on an i7), if it has closed, and there are no remaining Valve Processes in Task Manager (Steam Client Service and Bootstrapper) we can move on to the next step, if not (Program remains open despite significant time, I'd go as far as a few minutes) Go ahead and End Task it through TaskMan.

If it has closed: Try to send your pc into sleep mode. Then wake it and power down (Shut Down), and restart. Now try starting up Steam again. (There's more we can do if this has no impact)

If it has not closed: This could point to a larger problem. Have you installed the current drivers for your Nvidia Card? Have you installed the current version of the VC Redistributables, .NET, Windows Installer, and DirectX? Be sure to run Windows Update after installing these programs:

Microsoft Visual C++ 2010 Redistributable Package (x64) : http://www.microsoft.com/en-us/download/details.aspx?id=14632
Microsoft .NET Framework 4 (Web Installer) : http://www.microsoft.com/en-us/download/details.aspx?id=17851
Windows Installer 4.5 Redistributable : http://www.microsoft.com/en-us/download/details.aspx?id=8483
DirectX End-User Runtime Web Installer : http://www.microsoft.com/en-us/download/details.aspx?id=35
Nvidia Drivers : http://www.nvidia.com/Download/index.aspx?lang=en-us

Again there is more we can do if we are not successful, but please try these steps first.

[DreadedX]

All drivers are up to date. Steam.exe still remains open in the task manager after you click to open the program but no UI appears. The only way to close the process is to manually (force) restart the computer. The only way I can use Steam again is to delete everything in Steam folder (except the exe) and let it redownload all the files.

[blkmnky]

Is this only a problem with Steam.exe, have you noticed any problems with other programs or games? Have you done anything different with your computer on that Thursday or Friday? Could you reseat the cables attaching your SSD to your Motherboard.

Do you know how to edit the Windows Registry? The instructions for correct manual uninstallation are here, at the bottom: https://support.steampowered.com/kb_article.php?ref=9609-OBMP-2526

You'll want to be sure Steam.exe and the Client Bottstrapper.exe are both closed before you attempt this. My guess is you'd restart before you start the above to avoid the open processes. I will stress that you should always cut and paste the steamapps folder to another place before you attempt this, (it's the location of all your games) this will prevent having to download all of that again.

After a restart then please download the client from : http://cdn.steampowered.com/download/SteamInstall.msi
After everything is installed, ran and logged in, exit steam from the icon in the Taskbar on the bottom right (your Tray). Now place the steamapps folder back into the Steam folder. Now restart Steam.

[DreadedX]

SOLVED: I can't believe it but it turns out it was Ashampoo Anti-Virus all along! I had only installed it Friday but I never would have thought it would have been that stopping it from opening. I have sent them a message about this and hopefully will get a fix for it ASAP. I have gone back to using Avast now.

Thanks for all your help/insight.