Error opening the file. There may be a disk or file system error. Most of the time, I have to search extensively on the Internet about these problems, but yours is a dead giveaway. You've got a big ol' virus or, more precisely, a big ol' worm.
Worms use parts of an operating system that are automatic and usually invisible to the user.
It is common for worms to be noticed only when their uncontrolled replication consumes system resources, slowing or halting other tasks. Basically, a worm is a virus, but a virus isn't necessarily a worm. I am a die-hard Macintosh person currently on my eighth Mac, plus two iMacs we bought for our daughters. That leaves two older pre-G3 computers, two printers, a monitor and three 56 kbps external modems, all in working condition in various closets at our house. They seem too old to sell but too good to throw out.