[WhoCares]

I'm using IDA v5.2. It can identify XP SP0 symbols but can't identify XP SP3 symbols. Don't know why.

I downloaded "WindowsXP-KB936929-SP3-x86-symbols-full-ENU.exe" and extracted "ntdll.pdb" to system32 directory(sure current OS is XP SP3), then loaded ntdll.dll and ntdll.pdb with IDA. It could't identify "sub_7C93B077" as "LdrpInitialize" though it said "total 1016 symbols loaded" in the log window.

But the same procedure works for XP SP0 ntdll.dll/ntdll.pdb.

BTW:
IDA v5.4 can use windbg engine now:
_http://www.hex-rays.com/idapro/debugger/windbg_tut.pdf


Edit:
Finally I found the answer: just create an empty directory "symsrv.yes" in IDA directory, it will load SP3 pdb symbols.
_http://hi.baidu.com/0xfei/blog/item/9c74aad9f710f4ef39012fa4.html