To answer your second question first: you need to make sure you have a firewall running. XP (with Service Pack 2) has a decent firewall that will block remote connections to your PC, except those that you specifically want. the firewall settings are in your control panel, under 'Windows Firewall'. The exceptions tab lists those programs or ports that you allow remote connections to.
If you can't set your firewall settings then you don't have administrative privileges. You can check your profile in the 'User Accounts' dialog (available from the control panel). Again, if you don't have privileges for this, you aren't an administrator.
If you are sure that you should have administrator rights, but can't manage your firewall or user accounts, then a reinstall would be the safest course of action.
Make sure that you are running an Antivirus package; it will protect you from malicious programs that you unwittingly downloaded to your computer.
If you can't set your firewall settings then you don't have administrative privileges. You can check your profile in the 'User Accounts' dialog (available from the control panel). Again, if you don't have privileges for this, you aren't an administrator.
If you are sure that you should have administrator rights, but can't manage your firewall or user accounts, then a reinstall would be the safest course of action.
Make sure that you are running an Antivirus package; it will protect you from malicious programs that you unwittingly downloaded to your computer.