NT/IE5.5: Clearing cached web password?

I am Using NT4.0 and IE 5.5.
For some reason I am suddenly unable to access a website.
The error is: that my (stored and until recently valid…) login and PW are not correct.
I need to clear the stored combination.
Have searched everywhere,but can not find the correct info :-(.

So big Q: Where or how can I do this?

Tnx in advance