ID Change Won't Change on iPhone

I had to change my appleID as I cant access the email account it was originally set up on. I also cant remember the password that was associated with the old account as it was alwyas just "remembered" on the PC.

Changed OK on my windows pc iTunes but it wont change the ID on my iphone and I cant update my apps.When I hit Update on the AppStore on my Iphone it brings up the old ID and I cant seem to get it to change...I cant find the old ID in any of the settings in the iPhone. I have also tried syncing the phone with the PC : it syncs fine and updates but when I then access the AppStore on the phone, the old ID still comes up when I try to update the apps.

Any ideas of what I can do? Thanks for your help.

Cheers

Martin