In the Task Manager > Processes tab, you should be able to see each process and how much disk they are using each. You can click on the column header (disk) to sort process usage from highest to lowest.
The thing I must say is that you may be running the same software on all computers that were hacked. A favorite thing hackers do is infect one key piece of software that he knows you will continue to use on every computer so that you re-infect yourself every time.
Secondly, could you go to...
So when you type in the letter R, it becomes "RRRRRRRRRRR". is that correct ?
It is just that I have never heard someone describing the text in a textbox as 'scrolling'. I've been helping people on this forum for 10 years.
Try disabling your browser plug-ins one by one.
Even though you say it happens also in explorer, the browser is still active in a background window, (say you switched apps and make another one in front )