Links

Diagnostic:
Core Temp
CPU-Z
GPU-Z
Crystal Disk Info
OCCT
HeavyLoad

Cleaning:
Wise Disk Cleaner
Wise Registry Cleaner

Repairing:
Try SFC /scannow from CMD.

Graphics editor:
Krita
GIMP
Paint.Net

Text editor:
LibreOffice
AbiWord
Notepad++

Anti-virus:
Malwarebytes
Comodo Internet Security
Kaspersky Security Cloud – Free
VirusTotal

Other:
Net Disabler
Spybot Anti-Beacon
Revo Uninstaller Freeware