Is my USB memory stick dead.

As title really.

Plug it into an XP machine and when I try to open it in windows explorer it tells me it is inaccessable (bear in mind its in a different language!)

On W7 it tells me I need to format it on inserting the device. Windows explorer tells me to insert media on trying to browse it. I can't format it.

Its one of these from scan and has been working fine until now. The unti is incredibly light and the cap is very easy to lose. I have applied for RMA with scan.

http://static.scan.co.uk/Images/Products/1146183-a.jpg
16GB Super Talent DE-RBK, Black, Small USB2 Flash Pen Drive High Speed 150x

you have probably already tried another USB socket? or tried to access it from another PC?

I killed my Corsair 8GB when I plugged it into a front USB socket on a machine, later found out the socket was not connected correctly :(

Now I only plug my USB devices into the motherboard mounted USB's on other peoples machines.

Maybe the memory chip inside it is not accessible for some reason.

After a killed mine it was not recognised by a correctly wired USB socket - It just said Unknown device (or something like that)

Laptop (XP) and my PC (W7). Funnily enough it was a front USB port!

I did have problems ejecting form my PC so removed it after powering down as windows didn't seem to want ot let go.

Sounds like the memory chip died.

3 common issues with memory sticks,
1- memory chip dies, insert media is a common issue, what's happening is the pc is talking to the controller chip in the pen driver ok but it cannot talk to the memory chip, dead memory chip.
2- Controller chip dead, ether totally dead with nothing happening when you plug it in or you get unknown usb device and can get no farther.
3- physical damage, both faults 1&2 can be caused to damage to the pen drive or bad soldering however the common fail point is the solder joints between the pcb and the plug. If this is the fault and you don't mind voiding warranty, then opening up the pen drive and resoldering the contacts is possible.

There is a 4th type of fault I've spotted recently, another variation of physical damage, the chips and pcb's have got smaller but the same plastic casings are used, normally with just a thin additional bit of plastic inside the case to act as a back stop.
Needless to say this backstop quickly fails and the whole pcb&plug drop inside the casing (like a retractable dive), again easy to fix, open up the case reposition the pcb then put something behind it to stop it from pushing in (used little off cuts of wood here at work to repair pen drives broken in this way)

This is why I keep telling people not to only keep important work on their pen drive, they are good for moving data from one pc to another but not long term storage.

Thanks peeps I'll try and send it back.

Yep, I'm on windows 7 anad it told me the same about reformatting. I've learnt not to use it long-term, it's too risky.

Also found my friend's was apparently "messed up" by being inserted incorrectly into my laptop. I think that was to do with not shutting down properly too. I'm not saying this is your problem, but another thing to be careful of.

Another thing to be aware of is that there's quite a few viruses around now that target memory sticks :(