Windows Live Mail doesn’t get all my emails, only some

I have recently upgraded to a new PC running Windows 7 64 bit and using WLM to get all my emails now that I can't use Outlook Express. I have used WLM before on a W7 64bit laptop and it's get all my emails fine. WLM on my new PC will only get about half the emails that it are in the email (Orange) account. I have compared the setup details on both computers, and as far as I can see they are identical. Can any body suggest what the problem might be, it can't be the PC, can it................? Any suggestions would be greatly appreciated before I get so fed up, I  reinstall XP to use OE. Thanks.