I'm trying to use my $100 gift card and each time I try to make a purchase the only billing info is my credit card. I have entered my gift card number and $100 shows on the menu bar. I'm running Windows 7 on an HP PC. Can anyone help?

Hey Redritr,

Thanks for the question. iTunes purchases are billed to Store Credits first, before Credit Cards, as outlined by the following article:

When making purchases, content credits are used first, followed by Gift Certificate, iTunes Card, or Allowance Account credits; your credit card or PayPal account is then charged for any remaining balance.

via iTunes Store: How iTunes Store purchases are billed

http://support.apple.com/kb/HT5582

It also may be that the iTunes Store is prompting to verify your billing information:

When there is a mismatch between the iTunes Store's records and your credit card company's records, you will receive an error message stating that your credit card's security code isn't valid or that your zip code does not match your bank's records.

In most cases, this issue is caused by a formatting error in the billing address that you have provided. You can correct the issue by verifying that the information you have provided is correct, or by changing the format of your address to match the format that your credit card company has on file.

via iTunes Store: My credit card's security code or zip code does not match my bank's records

http://support.apple.com/kb/TS1646

Additional Information:

Why can’t I select None when I edit my payment information?

http://support.apple.com/kb/TS5366

Thanks,

Matt M.