Question about Outlook Express

I'm running WLM and Windows 8. In the Newsgroups folder it will only download 300 headers at a time; there used to be an option to change this (I used to have it set at 999 headers) but I cannot find where to alter this. The only option seems to be to click the 'get next 300 headers' button but I'd like to download up to 999 at a single go.