Rather than running without a firewall, make sure that the XP firewall's allowing LW.
User Cant Connect - LimeWire

Have you used LW from the dorm before? Any chance that the school's stopped allowing p2p use? Can other people use LW at school?

Delete LW's preferences folder when LW's properly closed. See point 3 here & also point 2 if you've used older versions of LW in the past (there could be a folder in either location).
Fixes for LimeWire
This will kill all of your settings within options, you'll have to go back through afterwards & reset things. If you're not sure of your settings, go through LW's tools > options & write them all down, so that you can reset things later.
In case you're using Vista: LimeWire Pref Folder in Vista

What version of Java do you have? Try this version. Download the JRE offline installer & remove any other Java versions before installing this one.
Archive: Download Java 2 Platform Standard Edition (J2SE) 5.0 Update 11

In LW tools > options > advanced > firewall config. Change LW's listening port to 64049 (or try others in the range of 49152 - 65535) > apply > ok.