Windows 8 suddenly slow

Hello forumers on this forum. My computer has suddenly run very slow and will only function as it did before in safe mode. I'm not sure whether it's a virus or something wrong with the system but I need help urgently because I use this computer for work. I have scanned my computer with malwarebytes, avast, tddskiller in safe mode to no avail. I have also gotten some of my colleAgues to do make some changes and although they have made it faster by uninstalling some programs, cleaned my comp with ccleaner and disabled some start up program's my computer is not the same as it was before with general slowness and constant freezes.

Please majorgeeks I need your help.

 

Edit: my disk usage is at 100% constantly with seemingly no culprit in tAsk manager. My specs are.

Windows 8 64bit
Processor is amd fx 8150 eight core processors 3.60ghz
Ram is 8gb

 

Yes I have