Unable to compile EP20K300EQC240-2X device using Quartus 9.0sp2 Web edition on Windows XP.

If you buy a fixed NIC ID license for a single machine from Intel / Altera, they still allow you to use the Quartus tool on two other machines (like having a home, desk and lab machine, all being used to work on the same design). The Intel Self Service Licensing Center generates the appropriate license.dat file when you provide the NIC IDs for these companion machines. You can read the documentation on their website about companion licensing.