I used the Visual Studio Dumpbin program to dump the exported api's of relevant Winsock DLL's, on both Win98SE and WinXP. The results are shown below.
On WinXP, if you hook wsock32.dll, most of the API's are forwarded to either ws2_32.dll or to mswsock.dll. Only a couple API's are handled directly.
On Win 98SE, both wsock32.dll and ws2_32.dll handle API's directly. I think, but am not sure, that wsock32.dll is Winsock 1 (which you use by including winsock.h) and WS2_32.dll is Winsock2 (which you use by including wsock32.h). MSDN has a whole explanation about this, I also think the Winsock FAQ has a lot to say about it: http://tangentsoft.net/wskfaq/