Cant complete any downloads,

If so, boot up with that and choose "R" at the first menu, that will get you into the recovery console, from there, at the prompt, type in "chkdsk /r" without the quotation marks.

Let check disk run, it may take some time, but when it's finished, type in "exit" and let the system reboot. Hopefully it will fix any system files that may have gotten corrupted.

If that doesn't work, post back.

Good Luck!