It's not kept in a file that you can run around on your harddrive and find without spending a fair amount of time and coming to the conclusion that it's a pain in the ass. It's cached, waiting for you to dump it into a program.
Try this...
print screen
hightlight some text and copy that.
Open the Paint program and choose the paste option.
In theory, the text will be pasted, not the picture. Of course... anything's possible with a computer that does it's own thing whenever it wants to. 😀
Nik