hi there lingzero, welcome to geeks to go.
Sorry about your mishap but it is easy to do.
I accidentally click "OK" on one of their popup windows...then the computer starts to go wacky...
I fear you've accidently installed some malicious software on your computer. You are right about nail.exe but I suspect more malware was installed than just nail.exe.
Nail.exe is a is a hijacker which means it will intermittently change your Internet Explorer settings / Desktop to the link of it’s author’s sponsors. This program is usually installed through consent, however is sometimes packaged as another product. It is a registered security risk and should be removed immediately.
With that in mind you need to follow step by step then instructions here
. These instructions will ask you to download and use some software do this and you may clean up most of your problem. You will also be asked to post a hijack this log in the malware section of this forum. Do this and malware experts will help you remove whatever malware is left.