[16:17:33] [INFO] JavaFinder.parseWinJavaVersion:105: Java Version: 1.5.0_06 sorted as: 1.5.0_6 32 Bit Java at : C:\Program Files\Java\jre1.5.0_06\bin\java.exe
[16:17:33] [INFO] JavaFinder.parseWinJavaVersion:105: Java Version: 1.6.0_23 sorted as: 1.6.0_23 32 Bit Java at : C:\Program Files\Java\jre6\bin\java.exe
[16:17:33] [INFO] JavaFinder.parseWinJavaVersion:105: Java Version: 1.7.0_51 sorted as: 1.7.0_51 32 Bit Java at : C:\Program Files\Java\jre7\bin\java.exe
[16:17:33] [INFO] JavaFinder.parseWinJavaVersion:105: Java Version: 1.7.0_51 sorted as: 1.7.0_51 32 Bit Java at : C:\WINDOWS\system32\java.exe
[16:17:33] [INFO] JavaFinder.parseWinJavaVersion:124: Preferred: Java Version: 1.5.0_06 sorted as: 1.5.0_6 32 Bit Java at : C:\Program Files\Java\jre1.5.0_06\bin\java.exe
Uninstall all versions of Java other than 1.7.0_51.
Also, since you're using an old XP machine with 2 GB of RAM total, the only 1.6.4 FTB pack you will be able to play is FTB Lite 2. Your computer just doesn't have the available resources to run the other 1.6.4 FTB packs. You can also give the older packs a try and see if those work.
Edit: I just noticed that you're trying to run Unleashed, which is for 1.5.2, so hopefully once you uninstall those old versions of Java, things should work out okay for you.
Also, try lowering your RAM usage to 1 GB; I don't think you have 1.5 GB of RAM free, which is also causing an error.