Welcome back, I am a Windows 8 user myself and Portal Injector, PerX, and Extreme Injector has been working great for me.
https://www.mpgh.net/forum/292-combat...edibility.html
https://www.mpgh.net/forum/292-combat...or-v2-1-a.html
https://www.mpgh.net/forum/292-combat...-injector.html
Basically about 80% of the injectors released here will work with Windows 8.
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