Big Pistons Forever,
Your ISP is completely separate from your PPRuNe Account. You can log into your PPRuNe account from anywhere.
If you are looking to change your email addy in your profile:
Click on User CP >> Edit Profile
And in there you will find where your email addy is located. You can change it and then hit the Submit Modifications Button at the bottom of the page.
Take Care,
Richard