Changes to my family's computer caused computer to not start?

I’ve never had this happen before. But my family member tried to turn on the computer a few times and it wouldn’t come on at all and then just recently it turned on and it said:

“Unable to start because of changes made to your computer.”

It then did started to search for repairs, but my family member canceled it and the computer seemed to work fine, except the “scroll bar” (Or whateverthat thing is that you use to scroll up and down pages on the net) was a little laggy/slow. But all our files etc… Was still there.

But the night before this happened my family member tried to play a MMORPG that we have had for over a year (So we trust it) but a pop-up showed up that said “downloading” something, not sure what (according to my family member). But according to my knowledge that pop-up that was “downloading” something was just something that prevented hacking in the MMORPG. It is called X-trap I believe.

But soon after it “downloaded” Windows Defender told us that changes have been made to our computer. I “denied” the software and Windows Defender said I had to restart the computer to get rid of it. I also did a up-to-date MBAM quick scan on it and it found nothing. I also have Avast 5.0 and it hasn’t found anything.

What causes this? Malware? Maybe our computer had some kind of “failure”?
And can this travel to other computers? (I realize this is a dumb question) I don’t want my other computers messing up like this.

Thanks in advance!

X-Trap is an anti-hacking software owned by nProtect that is used in MMORPGs like Cabal to prevent hackers from hacking games and it’s not compatable with Windows 7, only XP. It’s about the same as nProtect GameGuard.

Some anti-malware and anti-virus vendors flagged the program as a trojan.

Is it malware? Or is the anti-virus programs/vendors just mistaking it for that?

I don’t think that’s why the computer wouldn’t start though, unless it really was malware?