need to get into windows xp for ubuntu to recognize my external HD?

[dinbrca]

I have an external 500gb HD and if i restart the computer and insert the HD then ubuntu says: "cant mount.." it means he didnt recognized it so what i need to do is restart the computer.. get into windows xp so it will recognize the external HD and then restart the PC and get into ubuntu and then it works...
that weird.
thx for the helpers.
BTW:
my external HD is:
WDG1SU5000EוWestern Digital
USB 2

[Rocket2DMn]

Did you make sure to Safely Remove the drive from windows before unplugging it?

[dinbrca]

yes.. but i dont think it is matter..

[Rocket2DMn]

OK, can you please post the complete error for me?