Hi Nanci.
I guess you don't belong to the "what does this button do?" category, so I'm gonna talk more abbreviations with you.
My first suspicions are (although I don't have much experience with IBM machines) that the problem you are experiencing is most likely to be a "safety switch" in your BIOS or Windows. Safety switch regarding the fallen fan. You say that it was connected by 3 pin wire, that tells me that it has RPM monitor (which is redundant for chassis fan), while the molex fan doesn't. I imagine that your problem started with the fallen fan (that obviously stopped or got jammed), and now the BIOS isn't getting any feedback. (0 RPMs). This you can check in BIOS ("Advanced power management" or something).
2nd thing to try is to boot in safe mode (f8), but first choose "enable boot logging". After the system freezes, restart to safe mode and find "ntbtlog.txt" file in your windows dir. There you would find what's causing the stall. 90% chance it would be the last entry.
In such scenario, my guess would be the ACPI.sys. That is the Achilles heel with XP. Thing is, there is a setting in BIOS called "ACPI/API" that can be enabled/disabled (also in "Advanced power management" section). You must not change it after the XP installation is complete. Once the XP is installed it will only work with that setting as it was when the installation took place, doesn't matter if it was enabled or disabled. Changing it would cause windows to be unable to boot even to safe mode.