winapi - logonUser not supported

i desperate. my applications run as windows service, and it needs to create new regular process with different credentials. it should run under win nt, xp, 7, etc. because it runs as a service, i have to use the logonUser and CreateProcessAsUser win api functions (and not CreateProcessWithLogon).

on win 7 + win 2003 server it works perfect, but on win xp i got error code 50 while invo开发者_如何转开发king "logonUser" ("the request is not supported"). i tried to play around with the local security policy, but it didn't work.

any suggestions?

(i invoke logonUser with default provider flag (0) and logon interactively (2)).

EDIT: the problem is probably not windows xp. i run the same code on other win xp machine, and it worked. so, it is problably specific configuration on specific machine. maybe the i changed some configurations while i was playing with previous problems (http://stackoverflow.com/questions/6898361/createprocessasuser-win-api-is-not-working-on-non-win7-platforms)

therefore, maybe my question should be: what configuration can effect the logonUser function, so the error message "The request is not supported" can be raised?

p.s. i cant be sure that logonUser was successfully completed before, but i think it does.