Peter,
Welcome to SevenForums.
Did you perform the sfc /scannow? Yes/No.
There are many possible causes of your present situation.
If you disconnect from the internet, is the computer still slow? Yes/no?
If you boot up into SafeMode, is the computer still slow? Yes/no?
That's three questions, please answer all three.
Ø Power down your computer.
Ø Power up your computer.
Ø IMMEDIATELY—Start tapping the
SPACEBAR Ø When the
Windows Boot Manager screen appears,
Press the
F8 key
Ø The
Advanced Boot Options screen will appear.
Ø Using the down arrow key, highlight
Safe Mode Ø Press the
ENTER key.
In shorthand,
PowerUp | Spacebar until
Windows Boot Manager | F8 | Safe Mode | ENTER