Hello there, can anyone help me. I have a hotmail account and I believe it has been hijacked. Can anyone give me some advise please.

It depends what you mean!

Can you still access your account?
If so, change the password.

Otherwise:

http://support.msn.com/eform.aspx?productKey=hotmail&page=support_home_options_form_byemail&ct=eformts

What cgk said.

Is it that you've started to receive non-delivered email notifications? In which case it could be that somebody, who has you as a contact in their address book, has a virus, which is sending out emails "from" all the email addies in that address book to all the email addies in same address book. There's a new variation of the Storm worm virus, which has been in circulation for the past week or so.