I am going to be setting up an online business that will expose high-value data, i.e. trade secrets, IP, merchant/e-commerce accounts, etc.
The computer has been used before for looking at porn, etc. I had malwarebytes but I know this computer is probably compromised despite finding nothing on scans.
I am not super tech savvy but I know enough to at least get started in the right direction. Before I proceed with using this thing for anything valuable, I wanted to install a new security suite/VPN. Before I do that I want to really clean this thing up. There are all kinds of weird phenomena unknown "users" and connections, and can't access/delete some files despite being admin; just fishy stuff that I'm sure some of is actual normal system processes and operations. I'm sure there is something/someone(s) skulking around my system/network.
Before I go about (attempting) to install and set up this thing properly for a secure private business, how do I really get it clean without a bootloader something or hack coming along as a "stowaway."
I could do "reset" but I'm not sure that is enough as I know anyone with the right skills can even get around that. What should I do?