SBS 2003 Domain Name vs NetBIOS name

No, Not with the (modern) clients.
There will be apps, once again few modern ones, that won't work. But that isn't the only consideration. There are certain functions that won't work, predominantly from the command line. Most of this stuff should be all related to the netbios/beui emulation and support. However, that runs deep. The core of the OS still speaks LANman. Since it's 2003, if possible, rename the forest and domain. You will always have lots of little niggly issues, some functions that won't work as expected. I'm an old CLI nut, and most of your functionality there will be curtailed. Even your scripts will have issues.
Think back to the problems you used to have with LFN support in NT/Wintendo. While it works, some programs couldn't save rght, and with multiple similiar entries, the ...~1, etc, is a nuisance. These kind of issues will plague you, for many of the same reason.

For clarification, ask someone that runs a L/Unix environment. Wintendo clients will work in domains that use names that don't adhere to the netbios limitations, but they have issues.
Good Luck!

Thanks for your prompt response Casca1.

This is SBS 2003 OS so renaming Domain is (supposedly) not supported, which is why I'm currently reinstalling SBS2003. The previous Domain name was only 15 characters while the new one is 16. I'm correcting a wrong Domain name with the right one, but the new name's length may be problematic down the road. However, everything running on this server will be latest and "greatest" versions of all applications. This is a Small Business installation with no IT dept. except for the likes of me (equipped with a premium EE account and a degree in difficulty from the school of hard knocks while working towards my PHD in same). Therefore, I don't anticipate missing any command line functionality or some of the other ("greek") things you mentioned. I'm mainly concerned with Symantec VPN Client, Winternals Recovery Manager, SharePoint, Exchange Server, etc.

Thanks again,
Brian

One point of clarification:

The Domain is AbcdefghijklmnOP.local while the NetBIOS name is ABCDEFGHIJKLMNO per the installation wizard default truncation.

Regards,
Brian

There will be absolutely no problems. The FQDN of your AD and the NetBIOS name of your domain are two completely independent names. Your AD name can be sense.and.sensibility.movie, and the NetBIOS name RAMBO; it won't matter.
What you might want to do is to change the NetBIOS name to something that is not, well, "spelled incorrectly".
The only time you have to pay a bit of attention to this is when entering credentials, for example when mapping a network drive with different logon information.
You can mape the oldfashioned way, NetBIOSDomainName\UserName, or using the user principal name, usually user@your.domain.local.

>You can mape the oldfashioned way, NetBIOSDomainName\UserName, or using the user principal name, usually >user@your.domain.local.

Actually, both are valid UPN methods.

While there shouldn't be many issues, I have to disagree with you on the aboslutely no problems.
There will be some problems. Will the be major? Not likely. But truncated names DO cause an issue.

UPN is the User Principal Name. The UPN is only defined and can only be used in an AD domain, and it requires a client running W2k or later. The NT4 Lanmanager logon with NetBIOSDomain\Username can be used on NT4 as well as on W2k or later, in an AD domain, or in an NT4 domain.
As I said before, this NetBIOS domain name is in no way "truncated"; this is only a *suggestion* by the wizard, and it can be changed to whatever you want your NetBIOS domain name to be. Again: The NetBIOS domain name and the FQDN AD name are *completely* independent of each other. This has nothing at all to do with long file names.
So, no, there will be no problems at all with scripts, command line programs, GUIs, or anything else (unless someone tries to authenticate as user@NetBIOSDomainName, but that has nothing to do with the NetBIOS domain name being "truncated", this is a user error).
An AD domain has a NetBIOS domain name and an FQDN domain name; the NetBIOS domain name is required for downward compatibility with NT4, and it is in no way connected with, dependent on, a truncated version of, or in any other way derived from the FQDN domain name.

So, when adding new Computers to the domain, what would I put for the Member of Domain: field in Computer Name Change dialoug entry, the Domain name or NetBIOS name? Or would you just put the NetBIOS name (i.e. ABCDEFGHIJKLMNO) and then stipulate the primary DNS suffix of this computer to reflect the Domain name (i.e. AbcdefghijklmnOP.local) and check the "Change primary DNS suffix when domain membership changes."?

For W2k/XP clients, the fastest way is to use the AD domain name. The NetBIOS should work as well, but this can take some time.
For NT4 clients, you'll still have to use the NetBIOS name.

The LFN was used as an example. You might want to consider your response before you decide to tartly respond.
Your Opinion may conflict with mine, but that doesn't necessarily make you correct. As had been stated, I disagreed with you. On the other hand, idiocy is it's own reward.
I admit I stand corrected on one point; The Domain\Username format isn't UPN. However, since you are so good to point out an error when seen, here's my pointer. As stated by the IETF, which sets the standards, It consists of a realm in the form of a valid, and unique, DNS domain name and a unique username. Since MS rarely adheres to Standards, even their own, it's understandable why the old LANMAN authentication methods are still used, and included as a logon process.
In addition, the netbios protocol truncates the name, and adds it's own bit to the end. But your right, that doesn't change the name UNTIL the last bit. It shouldn't make a difference, but it can.
In order to illustrate the distinctions, I used the referrence of LFN's. Should I have to explain that? Only to students.

FQDNs, SFNs, LFNs, etc... all belong to a vernacular I have yet to appropriate, but I certainly aspire to fully understand what the hell you're all talking about someday. Gratefully, this download of information, to an IT bottom feeder like myself, contained useful information I could comprehend and it has helped me move forward with the task at hand. I appreciate your efforts Casca1, but my question was specific regarding XP clients and oBda appears to have answered my specific question (and without any sarcasm i.e. "On the other hand, idiocy is it's own reward").

Best regards,
Brian Esser

Casca1: I posted question to share points with you at: https://www.experts-exchange.com/questions/21145145/Points-for-Casca1-Re-SBS-2003-Domain-Name-vs-NetBIOS-name.html

Oh, No, not at all; If I was off base, in either answer or attitude, then I wouldn't feel right. Thank you for the consideration, but please, if the question was more adequately served by oBda, then he deserves the full recognition.

Inflection is the hardest thing about text communication, and I'm happy to see that it was the lack of inflection that made it "sound" off base in my reading of it. Even more, I think you both deserve recognition. I'm indebted to the incredible contributors on this site and for you to take the time to give a reasoned response to my need is 80% of the grade.

Please, take the points, after reviewing your response ("No, Not with the (modern) clients.") you actually did answer my question in the very first sentence. I just got distracted with the rest of the post that mentions various things that I'm unfamiliar with.

You guys (gals) are the best!

Brian

Casca1: I posted question to share points with you at: https://www.experts-exchange.com/questions/21145145/Points-for-Casca1-Re-SBS-2003-Domain-Name-vs-NetBIOS-name.html