Slow system performance and boot issue

The boot process of this machine was just super slow and immediately after opening windows you could get advertisements, pops up balloons, and many other logos of various programs. Note that this before you clicked on absolutely nothing! We also had many error prompts on the screen. The computer functionalism went low and got worse because it took more than half a minute for windows explorer to start. This is after the computer had been fully rebooted. Applications such as excel also took almost 60 seconds to open. It was really slow. What do I do?

Application Error
Exception in module ct.exe at 000847A9. Unable to start performance monitoring. OK
