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.