I am having trouble getting the update files from QuickPayroll to run.  
The auto update downloaded the files, but they will not run, so I did a  
manual update, that file will not run as well.  I can run most other  
exe files OK.  What I have noticed is that the files that do not run  
also do not have information in the properties, like version and such.  
 
I have used file Anylzer to query for file information and these files  
do not have the same type of listings as other files.  (Lack of or  
incomplete version, PE sections, headers).  Question: is there  
something in XP blocking these files because of the lack of  
information? Windows security setting?
 
Update:  I found another file that I downloaded and it wil not run either, same lack of file properties.   I shut off everything that I could and still wont run ...weird.  Will run on the other machine even with everything turned on, only difference is the updates ...hmmm.  But which one?
 
This machine has all the updates, I tried the files on another machine  
with SP2 and no updates, and the files ran just fine. The only way I  
have been able to work around this is to do the updates on the vanilla  
machine and move the files back to the updated machine.  
 
XP Pro  SP2 - current updates
P4  2.53 GHz
2Gb  RAM
ZoneAlarm Pro w/virus and spy protection
Pest Patrol
anything else? let me know

one of your security apps maybe holding it from running. or already cleaned it.
 
try disabling za and then see if you can run it.
 
my money is on za, it always locks down everything as if the user is a 2 year old but I could be wrong.

That sounds feasible. If you're going to shut down ZA temporarily to test out Ed's theory, can you disconnect from the net?
 
I have Zone Alarm on hundreds of units, but just AV. No problems. Do you have ZA on the vanilla?
 
How does the Analyzer query see those now-working update files in vanilla?
 
Another avenue to approach: - exe files need clean dll's to open an app. Perhaps there is a malware problem on the update machine. The wackos out there LOVE to target dll's. I would send a HiJackThis report to spywarewarrior.com to eliminate that as a possibility. The engineers there are the best in the world. Go to their site for the info on how to do it.

Thanks for the intrest all.  This is a strange one to me, I have shut down ZA and all other progs. stopped all processes that I can without killing the computer, and still no joy.
 
Ran:
TrojanHunter
AVG Anti Spyware
PestPatrol
Spybot
ZA scan
HJT
 
only found a few, low risk threats.  I am thinking this a security issue because of the lack of header info in the file.  The file in question is a small frontend to 'unpack' the updates for my payroll program.
 
Just noticed an oddity, the A: light comes on for two seconds when I sit on a file name for a sec in explorer.  Dont remember it doing that before.

follow what pscowboy said.
 
in the mean while to shutdown everything you need to msconfig and shutdown all none ms services and startup apps then reboot then try and run the file. if you need a walk thru check here http://www.klitetools.com/MM/msconfig.htm
 
you can also try and see if its DEP
 
be sure to follow the steps pcowboy has suggested also he knows best

Hydro -  
 
For us to help you, we need all the questions answered. Please.
 
With ZA shut down, the exe's still didn't fire up. Only direct replacement of the updated files works. I don't think you have a security issue.
 
I'm thinking now you have non-critical kernel corruption.
 
You should file the report I suggested. One must always rule out foul play.
 
Then you should do a Repair install. Pop in the XP cd and get to the SECOND screen where a repair is offered. Do that. You won't lose any of your stuff, and XP will overwrite its' operating system.