Closing the "back doors" on my Windows XP Service pack 2? Advice?

[PhoenixFlames]

Hello people

I am clean installing my PC from scratch (which I can do- pretty easy done it before).

However I remember this computer security expert who went into my PC and closed all the open security doors.

Now apparently there is security flaws that potentially mean people can access your PC from the web because "doors" are left open (rumour has it Microsoft leave them undone so people get paranoid about PC Security and purchase expensive software.)

I know about turning on the firewall BEFORE going online (to avoid well known Trojans Worms that my PC is vunerable to online). Possibly starting PC in safe mode AND updating all security setting a.s.a.p.

However apparently there is a menu where you can close certain privaleges off to avoid remote access to your PC.

Any ideas. Unforutnately this computer expert said he would only help me once (god I only wish I wrote down what he said).