Hello Thinkpac,
maybe my experiences are of some interest, otherwise please excuse the long post. I understand you intend to do a factory install, but you may want to consider a clean install.
I don't have a comparison between a factory installed xp and a clean install of xp. My T61 came with vista preinstalled and even though SP1 made it a bit "snappier", it never compared to the clean install of xp (which was added) in terms of battery time and speed (both boot time and responsiveness). The two were light years away. Later on I clean installed vista, only to find out that it is just as responsive and efficient as xp when all the bloatware is left out in the first place (though boot time is still a bit longer)! Removing undesired Software after running a factory install did not have the same effect.
In the end, I called every Thinkvantage tool into question: do I really USE it? (potentially needing or experimenting with it is a different question). I ended up installing only the Fingerprint software and Power Manager (VERY bloated but as long as its window is not opened, it doesn't clogg the system. Its "extend battery time" feature was the reason for installing it, for it allows you to disable several devices and settings with just two mouse clicks). Even the long (and happy) relationship with Access Connections ended, when I realised that the only feature of use to me was the automated selection of the default printer. Everything else I use is equally provided for by windows.
After many clean-installs of both OS's I found that for both, the order of installing the following is VERY important (using the latest version):
01. windows os installation
02. Intel Chipset Support
03. Intel Matrix Storage Manager
04. all windows updates (SPs etc.) WITHOUT any of the suggested drivers! If a driver update is listed under critical or important (e.g. the LAN driver), install (individually) the latest Lenovo driver at this point for that device (otherwise certain updates, including service packs, may not be accessible). Ignore all the other driver suggestions from Microsoft. Search repeatedly for Microsoft updates until no critcal or important updates are left and all the service packs are installed (currently SP 3 for xp, SP 2 for vista).
05. Lenovo System Interface driver (SMIF) (important to install AFTER the os updates and before any remaining device drivers!)
06. Lenovo ACPI Power Management driver
07. Lenovo Display driver
08. Lenovo Monitor INF
09. Lenovo Wireless LAN driver
10. Lenovo Audio driver
11. Lenovo Modem driver (if applicable)
12. Lenovo UltraNav driver (NOT the UltraNav Utility)
13. Lenovo Hotkey driver
14. Lenovo Bluetooth driver (if applicable)
15. Thinkvantage Fingerprint reader driver and software (if applicable)
16. Lenovo Atmel TPM device driver (if applicable)
17. Lenovo Power Manager (if desired)
If battery drain during hibernation is an issue, check the following thread:
http://forum.thinkpads.com/viewtopic.ph ... 23&start=0
Good luck!
George
EDIT: Thanks to Franasia for pointing out that the LAN driver wasn't mentioned in the above list. In the above case, it was a precondition for the service pack and was hence flagged as critical under MS Update (step 04).