I figured out the problem as I was having shutdown problems as well. I had a battery dll from the slim drivers and it was never recognized properly.
It seems that the BIOS I was using (A01) was not being recognized as ACPI compatible. I was getting a message during the XP Pro install that setup could not detect what kind of computer it was and I had two choices: Standard PC with C-Step i486 and other. "Other" did not work and I was left with the i486 option. I got the idea about this here: http://www.theeldergeek.com/clean_insta ... ows_xp.htm
I did two things so I'm not sure which actually solved the problem. The first was to upgrade to BIOS A02. The second was to redo my nLite XP PRO CD and instead of leaving computer type as automatic in the unattended install options, I set it for Advanced Configuration and Power Interface (ACPI) PC. I changed nothing else in nLite and did a full reinstall, deleting the partition and doing a reformat.
Then I was able to install the battery meter switch, the unknown device went away with the battery device now showing up, and I have a battery icon in the taskbar. The wireless switch also worked after this, although I have since uninstalled it as I didn't need it.
As I mentioned I don't know for sure that the BIOS was the problem so it could have been my nLite install. All is now good and it's quite a snappy little computer with the 4 gb SSD
and 2 gb RAM. The slim drivers worked great for ethernet, wireless, and audio. I did use the Dell installers for the rest.