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So I just discovered the cause of my mouse's "random" lagging. I have a Microsoft 3500 USB mouse and a Seagate FreeAgent GoFlex 500 GB external hard drive. When the former is plugged in, everything is fine. But when both of them are plugged in, the mouse pointer slows down and lags a lot (or jerks).

All my drivers are up to date and I'm on Win 8.

Any possible diagnostics/solutions?

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Does this persist for as long as the drive is plugged in, or for a while and then stops? Where are they plugged in? On a laptop, dock, desktop? Which ports? Same hub? – AthomSfere Apr 3 '13 at 23:22
Yes it persists for as long as both the devices are plugged in. It's a laptop (Dell XPS 15z). USB ports. – None Apr 4 '13 at 0:06
Does your HDD have an external power supply? – cutrightjm Apr 4 '13 at 6:31
No it does not.... – None Apr 4 '13 at 16:19

sounds like the external hdd is either drawing to much amperage from usb, or the data transfer of the drive is keeping the usb hub too busy for the mouse to get its data processed in a timely manner.

Try using the external hdd on opposite sides of the laptop if possible by laptop design.

Does this happen with normal usb flash drives? if not does it happen while moving a large file to flash drive? if yes then its the usb hub going out. if no then you can move to the external hdd next.

does the external hdd produce the same result on another pc, (plug same mouse and external hdd into two closest usb ports on another machine and test) if the same results happens here then it is definitely the the external hdd. you could try taking the hdd out of the case and just plug it into a desktop pc to see if it is the drive that is malfunctioning or the external case enclosure.

If it is the external enclosure that is bad you may be able to get a replacement from the manufacture or buy a third party from or

If the result is that your usb hub is going out, do you have a pcmcia slot on your pc. you can get a usb 2.0 possibly a 3.0 adapter card that would eliminate this problem

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some usb hubs on laptops are replaceable, some are part of the mainboard. find your service manual to find out in detail. (or just open it and look :) – user213584 Apr 4 '13 at 4:46

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