Some chip on the motherboard failed.
Do try what others mentioned.
And in parting, your files are likely ok. I put the old HDD into some USB case when folk forget to backup.
As you may know already, the E521 has no PS/2 ports onboard and has pretty much rendered the machine an expensive paperweight since the USB ports have all ceased to operate. A lil bit of the machine can be found here
In any event, so yesterday I was replying to an email typing away just fine when all of a sudden the keyboard stopped working and Windows began to make the alert sounds it makes when you insert or remove a USB device for like 8-10 seconds straight. A message from Windows Vista popped up then that I failed to read exactly what it said since i was eying the ports and caught the last second of error message as i looked back up at the screen before the message faded away.
It said something to the effect of "the ports cannot work fast enough 'something something 2.0" or that it "can perfom faster 'something something' 2.0"
Next thing I know I try to click the message bubble in the windows taskbar to read it again but the mouse wouldn't move. Then I try to navigate using the keyboard and it didn't respond neither but i noticed all the light on keyboard(scroll lock - num lock - caps lock) were on and flashing off every 6 seconds. Since I have a plethora of mice & keyboards, I began to switch em out and would get the same result, power to the devices but no activity on screen. I thought it might've been the devices and connected them to my other 3 machines and they worked fine and dandy. Put them back on the E521 and they're dead.
I've searched online the symptons and apparently it's a common issue amongst owners on this model and have seem the finger being pointed the most at the motherboard. Attempts to follow suggestions from people like "remove battery & reset set CMOC" or "change 'such & such' setting in the BIOS" is futile because even during the boot phase, they keyboard still wont work despite me pressing F2 or F12. I have no idea how to use the machine since PS/2 ports were ingeniously left out. Thanks a lot, Dell...
So if the machine is waste now, I guess I have to accept it, but I want to know why would the USB hubs stop working. Is it a motherboard malfunction, the hub itself, maybe windows, what would cause it to cease operating?