ps
are you using cable or what type of broadband etc.
this is relevent because some isp's give you a statric ip address, and some give you rotating ip addressees,
so if you have broadband (whatever) where you connect/disconnect etc you isp assigns an ip address each time you connect, which is usually a slightly different one out of a block of ip addressses
but if you have cable, and do not connect/disconnect, and have a static ip address, then it will always be the same,
you can usually change this by going in to your settings and changing it to a rotating ip address, it will only change slightly as it will still be out of the same block of ip addressess
your (or anyones) ip address can quite often appear in a spam list , although its nothing to do with you, its just that someone else using the same isp has used the same ip address from the same block of ip addresses that your isp assigns