Built my nephews new rig but having problems with memory sticks.

The motherboard has normal USB 2.0 and also 2 new USB 3 slots. I could not get the first memory stick to work in any slot so I got another , tested it worked on my own PC, connected it to this new machine and it worked ok (in USB 2.0 slot) - moved it into USB 3.0 slot and nothing - totally dead

Is it possible I have somehow trashed both USB sticks?

I also tried an external hard drive - but that refused to work saying "USB device not recognised" - although I can access it via eSata quite happily so it clearly is not broken.

Does something need to be enabled in the bios?

No - checked that.

I disconnected the front USBs from the motherboard then connected an MP3 player via a rear USB slot and that worked fine so possible it was the front usb ports somehow causing an isssue?

The front USB ports are often connected with individual pinouts which are very easy to get wrong. My parent's PC was once "repaired" by a "professional" and came back with the front sound and USB ports all incorrectly wired, which did not impress me much.

It's possible that if the 5v is on the wrong pin then it will fry anything plugged into them. It's also possible that they could be shorting out the entire USB bus in some way. It's very common for several USB ports to run from the same 5v supply, so shorting one port will kill all of them.

I have managed to kill 2 sticks before before realising a PC I was working on has the front panel usb's were wired wrong.

Have you looked in the Computer management/Disk management to see if it shows up? Sometimes there is a clash of protocols and you may have to sort out the drive letter designation manually for the USB device.

Yeah tried that and it does not show up at all

Got an old works spare memory stick which I will try tonight now I have disabled the front/top USB connectors.

I'd physically disconnect them rather than just disable them.

Yeah sorry - I meant disconnected!

Tried a works memory stick tonight and it was fine so (fingers crossed) thats cured it.