If ur not someone who tidies up your comp all the time you can get payment date off your statement and manualy look through your temporary internet files for the date near dates in quistion and get lucky or if thats no good phone the card company and get the payment specifics off them google the company name they give and try and locate it that way. Also did they send u a email when u signed up (theoretically) it may still be lurking in your email box if deleted it may be kept in the deleted email section for recovery. Cant think of any other way but 1 of these should be sucessfull.