Accidentally hit shift for 8 seconds. Help

[Colonel Kataffy]

I was typing a paper on my dell lap top when I accidentally pressed down the shift key for 8 seconds. The computer beeped and a screen poped up telling me something about the keys. I hit cancel. Now when ever I try to put my cursor some where, it highlights a block of text. I restarted my computer. I opened the folder that had my word file. When I double clicked on the file, it highlighted a block of files and opened them all.

I don't know how I got this setting turned on, but whats worse, I can't figure out how to turn it off. I know very little about computers. Please help me.