Credit card payments are recorded as transfers
When you make a payment to a credit card, the payment is recorded as a transfer in Money - from the account you make the payment from, and the credit card you make the payment to.
You cannot assign a category to this transaction, as transfer transactions cannot have a category.
This is exactly how Microsoft Money is supposed to work, as if you categorized the transaction, you would start 'double counting'.
For example, suppose you had a purchase of $100 on Clothes on a credit card. If you subsequently paid off the credit card, and used a Clothes category, then you will have 2x$100 transactions in the Clothes category. Using a transfer means that you only have one $100 purchase recorded, which is how you should see the transaction in reports.
When you purchase an item on your credit card, you are borrowing against future earnings - the payment to balance that account . Paying off a credit card does not affect your total
account balance - you are moving money from one account to another, and this is the reason no category is used.