Re: Mouse stuck on startup
you can use the computer without a mouse for at least make backups on an external drive or network. XP has native support for USB mice, but try using a PS2 if you can. You have to start the PC with the PS2 mouse plugged in or it will not work.
If it doesn't, as it's a fresh install, it's probably a fault in the setup (either user or software caused), and I think it's time to waste another hour or so of your life re-installing
Re: Mouse stuck on startup
Try a different mouse, that will answer your question (about whether it's broken or not). see if there is no errors in the device manager. unintsall mouse drivers and see if the system redetects them. also Boot to safe mode and see if the mouse acts ok. If it does something else is interfering with your mouse (software or hardware).