When I first launch Firefox (version 4.x or 5.0), it works fine for the first few hours. If when I am finished for several hours or overnight, and I leave multiple windows (each with multiple tabs) open, when I try to start up again with unlocking the computer, I find it completely unresponsive. I have to either do a hard reboot or wait 3-5 minutes before even task manager comes up to kill Firefox. If I kill Firefox via Task Manager (and it takes multiple tries), the computer comes normally responsive the instant Firefox has been killed off. I have repeated the same type of browser usage with both Microsoft IE and Google Chrome, and the computer never becomes unresponsive. Here are the high-level details of my laptop: OS Name Microsoft Windows XP Professional Version 5.1.2600 Service Pack 3 Build 2600 System Manufacturer Hewlett-Packard System Model HP Pavilion dv9000 (EZ459UA#ABA) System Type X86-based PC Processor x86 Family 15 Model 72 Stepping 2 AuthenticAMD ~1607 Mhz BIOS Version/Date Hewlett-Packard F.1A, 10/25/2006 SMBIOS Version 2.33 Total Physical Memory 1,024.00 MB Available Physical Memory 86.69 MB Total Virtual Memory 2.00 GB Available Virtual Memory 1.96 GB Page File Space 2.33 GB Page File C:\pagefile.sys