Remove Pages from Header Menu

Dear WP community

I’m struggling to remove pages from the Header Menu in my WP theme. On another WP blog that i run, i have a WooThemes theme with a built in editor, where i could type in the page ID’s that i don’t want to be listed in the header menu. Now i am using a free theme which doesn’t have that option available. I’ve uploaded a screenshot to make it more clear: http://artbookaddicts.com/NCpics/Pages-in-Main-Header.jpg

Basically i want Page 1, Page 2 etc. removed from the header. Is there any way i can exclude certain pages from the header menu by editing the code?

I’m a complete coding noob so any help on this would be very much appreciated.

Thanks in Advance