Attachments

Hello,
I am a new member and would like somehelp please.
I use Windows2000xp and have just loaded Office 2007 and now find that my e mail Mozilla Thunderbird will not let me open any incoming emails wth attachments or when I try to send a email as soon as I click on attachements the Mozilla program is deleted from the screen & I have to relaod it.
This also happens if I try to click on Mozilla help !
Removing theOffice 2007 programs returns the Email to normal operation

I have tried all ways to change the security settings & have made Mozilla my e mail client to no avail !
If anyone can help I would be vey grateful as I need both programs for work purposes
Thanks

Geoffers