Replying to computer problem...

ait im here on my family computer, and a couple tihngs are pissing me off.

i think someone posted a problem with this first thing before......

in the upper left corner of my screen when im on the desktop is a little gray square or something, it looks like the corner of something, it only comes up wiht i open something while im on the desktop, like if i have winamp open there is the thing, same thing happens with instant messanger etc.

2)this might be related. but i cant install anything. whenever i download a program like a .exe file or something, i cant install it. with some files i get errors, with others i get other errors. i cant download zip files cause when i try to install winzip it gives me the same bull crap. different programs say different things but i cant install anything. anyone know why? it was fine like 3 weeks ago and i think i installed osmetihng and this started.

any help?> i dont wanna havta reformat the computer again
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