This is a sad little tale! And I'm not sure what there is to be done about it as you don't have a CD to do a Windows over Windows repair.
But here is a situation where it might be useful to be able to use the keyboard.
Firstly, the Windows key (between left Alt and Ctrl) should get you a Start Menu and your programs.
Then, if you can do that, you should be able to find the System Restore in Accessories>System Tools.
If you can do that, maybe - just maybe - you can Restore to a point before Armageddon.
Even in my daily use of PCs, I'm about 50/50 Keyboard/Mouse. It can be so much quicker apart from being a rescue aid.
PS, instead of marking a wall, have you considered a hide-faced mallet or a 4 pound clout hammer?