Freeze on startup os often a software conflict with a driver/service.

If you have ever boot into safe mode I suggest doing that to see if it will allow you to boot into windows at all.

F8 on startup, select it from the menu.

Once you are there you can look at the boot.log file (open with notepad if it asks) and see where it stops. Or you can just do a simple scan disk and have it automatically fix errors, which will force it to do it upon startup and typically fixes errors like this.

If it doesn't solve your issues the OS might be corrupted. You can solve this by doing a repair installation or utility from the XP disk.

These are the simple fixes for an often complicated and time consuming problem of not booting, but its a good starting point if your not to experienced with this sort of thing.