[Arralen]

If someone from the internet is accessing "various ports" on your PC which connected to the internet through a router (router, not only DSL modem?), the router must be seriously misconfigured: Normally, it should drop any packets from the internet that where not explicitly requested from your PC (and thereby making a Personal Firewall superflous ..) - Unless you have forwarded special ports to your PC, to make it possible to someone on the Internet to access some server you're running.

Having multiple ports 'probed' sounds to me like you activated the DMZ (demilitarized zone or something, completely nonsense name for "let everything go right through"). This is a very bad idea in 99,98% of all cases .. as it takes your best security layer away and leaves you at the mercy of some 'personal firewall', virus scanner and security holes in those, the underlying OS and all the applications you're using.

Btw.- which OS and patch version are you using? There where several attacks on Windows which worked by deliberatly crashing the OS by sending malformed packets and getting some injected code executed on the way.

That said, you can't ever be 100% sure this was or wasn't an (un)succesful hacking attempt. I hope you're running the PC as user with restricted rights (only applies to W2k and XP prof, obviously)? If the answer is no, I give you a 67% chance that your PC is infected and needs reinstallation from ground up.