如果没有Virus，不要换电脑，本人分析如下：

蠕虫进入电脑偷信息的可能性极小，因为技术实现上难度极大。况且credit data may
not be in the files of computer, no one put that in the file actually. 有
一种可能性是online ecommerce, 即you lost your credit information when online
order. 本人是online ecommerce expert. There are two models online stores
charge your credit card when your order online:
1) 当你online order时，web server不存你的credit data,它只是转发给commerce
center.待transaction完成后，web server only has your order data without
credit card data. 不存你的credit data 主要是主人不想找麻烦。
2) 当你online order时，web server or some where keep your credit card data
when you come back and you don't need to input your credit card information,
such as Amazom.com. 一般各公司都有安全措施。但谁也不敢保证100%没问题。
本人估计问题可能在这里。
建议只用一个credit card does online order.并密切观注this credit records.一
旦有问题，马上更换。So far we don't know the better way to solve this problem
because you don't know  where the credit card data lost.