I was hesitant to upgrade from Python 2.5 to 2.5.4 on because upgrades usually break something.
I tested it first on a desktop. The default upgrade installed to a C:\Python25 directory and a lot of things broke. Python scripts that worked before stopped working.
easy_install would not work because it could not find Python.exe.
This was due to my previous Python installation was on c:\1Programs\Python.
Fortunately I created a system restore point before the upgrade and I restored to the point.
At this time, Python was still not working properly - the restore did not repair everything. So much for Window's System Restore.
Then I installed Python 2.5.4 again, this time on c:\1Programs\Python.
Now, everything works!
Lessons learnt:
1. Test the upgrade on a test machine first
2. Install upgrades on the same path of the original installation
3. Don't count on Window's System Restore Points