So I'm trying to install 10g on my XP Pro development box, and the install goes fine (I do the basic install of enterprise edition, I'm by no means an oracle expert) and when it gets to the part where it wants to create a database, the database creation assistant fails saying first that it cannot retrieve credentials, and then that it can't connect to ORACLE (I'm assuming this is the instance name).

Anyone have *any* idea what's going on here?

You probably missed the part of the installation where you give the "system" and "sys" user passwords.
this means that you should restart (more carefully) the database creation part.
You can choose the database creation assistant in order to do that, you reach it by clicking somehow like "start", "programs", "oracle orahomeXXX", "database creation assistant".
You may also consider de-installing oracle, (click on the "runinstaller", choose "installed products" and click "deinstall"), and restart the whole install from scratch.

I did all that before...my first instinct was that I fatfingered something, so I went through and reinstalled everything. I gave it default passwords to test it, but it wouldn't log in. I couldn't ev.en get PL/SQL to connect using the URL it gave me in the post-install screen, something about a TNS error. I researched the error and it ran through the fixes described (by removing NTS as an authentication service) but then I just got a different TNS error from PS/SQL+.

Oracle installs *flawlessly* on my Linux boxes and on my Windows Server 2003 box...not sure what it's problem is here...

The tns error means that the listener does not work.
there are no default passwords on Oracle 10, you must give a password like "nobody" or "mypassword", but you have to give one.
The winXP install for Oracle10 works exactly the same way as on Linux ! Simply the way the services are managed are different, in XP they are started from the Control Panel.

Control panel? Where in the control panel? Did I miss some oracle configuration control panel applet? I looked in the services snap-in and it didn't list any oracle services (unless it calls it something really arcane). I figure since the oracle installer offers to set up a database for you at install-time it should be pretty automatic and straightforward.

Yes, the install is fully automatic and straightforward, and you don't need to go outside the Oracle installer. However, if you go to the Windows Operating system control pannel in order to understand things, you should see the Oracle services started in automatic mode. If not, something was wrong in your installation, for instance if you do the install without being the Windows administrator.

OK, oracle didn't install any services at all...which is weird because I was running it as a Domain User in the local administrators group...do you think I need to be logged into a local administrator account?

Yes, sure ! You must be the local admin of this computer, and not a domain user.
Moreover, I'm afraid you cannot install it in a domain, maybe you should (just for testing purposes) try to install a standalone Windows system and try installing Oracle 10g on it.
You know, a RDBMS database server must be installed on a server system. You can cheat, installing it on a standalone Windows system, the standalone system emulating a server. But I'm even not sure you can install it on a client machine. Oracle server is traditionally installed on server systems, and Oracle client is installed on client system.
Please, keep us informed, if you were successful loggin on your own system as localsystem administrator, and if you were then able to correctly install Oracle.
If not, I strongly suggest you to restart everything from scratch (even on an old machine) just for learning purposes. After installing on a brand new Windows standalone system, you will feel more confident for installing it on your client system.
Regards
Yordan

I ran the setup using the SYSTEM account via PsExec and everything went off without a hitch. It looks like when run as a domain user (even if said domain user is a member of the local administrators group) it fails to set up the listener and the DBCA can't connect to the oracle instance.

It shouldn't have any trouble running on a workstation-class machine with 4GB of ram...the fact I'm using XP Pro and not Server 2k3 shouldn't make any difference with the exception of some optimizations having to do with timeslice quantas and resource allocation,

OK, glad to see that there are no more 10g install issues, and everything is working fine now.
So, we learned something from your adventure : we have to be system admin when starting and Oracle install on a Windows system.
Which is not fully the case when installint on a Linux or on a Unix or AIX box. On a Unix box, you prepare the install as system admin (rootpre.sh has to be fired by the "root" user), then you perform the whole installation as a standard user, and only at the end you have to become the system admin "root" user in order to fire the last install scripts name "root.sh".
Now, we are happy for you, enjoy your Oracle on Windows install.
Yordan