While Microsoft has fixed a lot of bugs and security problems with Windows XP Service Pack 2, there will always be some new ones waiting to be discovered and fixed. Without a lot of fanfare....

Microsoft has released a critical update for Windows XP Service Pack
2. They have found that if you are using the Windows Firewall included
in SP2 and you make a dial-up connection to the Internet, you may be
inadvertantly allowing file and print sharing with the entire Internet.
If you have Windows XP Service Pack 2 installed, you will need to get
the KB886185 update from http://windowsupdate.microsoft.com/.

Of course, that other bountiful source of bugs, Internet Explorer, was heard from this week...

The Security researchers at Secunia have posted details on another bug
in Microsoft Internet Explorer. In this case, a bug in the DHTML Edit
ActiveX control may allow a cross-site scripting attack, which may allow
a malicious website to put script into another browser session. They
say this affects fully patched systems with Windows XP Service Pack 1
and Service Pack 2. Secunia credits this find to Paul from greyhats,
and has also posted a test at http://secunia.com/advisories/13482/, to
see if you are vulnerable.

These bugs, and others like this, are covered daily at the BugBlog.