Errors after upgrade Win7 host, now cannot start anything

[OracleUser1]

Hi Virtual Box wizards,

Need you help !

I've been running VirtualBox 4.2.18 for some time. Today, when it prompted that a new version 4.3.22 is available,
I thought I'll give it a try and am since cursing myself.

My host is Windows 7 Home Premium on Core i7 with 6 gb.

I shutdown the VMs, then closed VirtualBox 4.2.18, then started installing 4.3.22.
At the end, it asked me to reboot, when I clicked OK; just when it was rebooting,
a window flashed saying the install had failed.

After it came back up, started VirtualBox, then I started a guest and it said "Cannot acccess the kernel driver".

I uninstalled VirtualBox, then re-installed the 4.2.18 (which was running fine all this time)
but at the very end, the same thing: just when rebooting, a window flashes saying the install had failed
and after reboot I can not start any guest.

I tried the whole process multiple times, made sure there is even no "Oracle" directory at C:\Program Files
before beginning install, but even the old trusty 4.2.18 wouldn't work.
and now I'm totally stuck.

I followed an old thread on the forum which asked to go into C:\Program Files\Oracle\VirtaulBox\drivers\...
and re-install the drivers, which I did, but nothing works.

What can I do get any version of VBox up so I can run my guest?

Thanks !

[here647]

The last one that worked in the 4.3 series was 4.3.12