Mouse and keyboard stop working in Windows 7

Today I have witnessed a rare problem with mouse and keyboard being unresponsive in Windows 7, even though they work in BIOS, boot manager, mini-windows, etc.

If this happened to you, it may be due to an unsuccessful upgrade or installation of Kaspersky Antivirus 2013.

The solution is quite complex and involves editing the registry offline, if you have never edited the registry before - this may not be a good time to start.
There are numerous guides online how to get into your registry when you can't do it from your system, I will not go into this here.

When you load your registry hive, you need to check two keys. The first key has the settings for keyboard:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e96b-e325-11ce-bfc1-08002be10318}

and it should have a string called UpperFilters and it should have a value kbdclass (if there are any other values, delete them).

Second key has settings for the mouse:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e96f-e325-11ce-bfc1-08002be10318}

and in the same UpperFilters string we should have the value mouclass (again, if there is anything else inside this string, delete it).

Here's an example of what it looks like when there is a residual erroneous key from Kaspersky inside the UpperFilters string for the keyboard:

That value "klkbdflt" is the troublemaker.