>  What I need to be able to do is:
> - Send a TCP SYN packet on a specified port.
> - Alter the IP header of the TCP SYN packet to modify the TTL.
> - Receive an ICMP message in return.

Can you explain the kind of application you are writing ?
I ask because this request is very special.

> Does anyone know of a way to manipulate the IP header within a request packet?

First, get hand on the complete packet itself. Tht's not what a socket 
can do, except on some special cases using raw sockets. You'd better work at 
the NDIS driver like a

> I figured the TCP Client component would be the best for this, but it doesn't
> appear there's any direct way to get down to the network transport layer to
> alter the IP header.

A TCP client handle TCP streams for read/write data. If you need to access the 
control informations,
you need to work at a lower level.

> Is there any way to do this?  Perhaps interacting with
> the Winsock DLL?

Not winsock (except raw sockets in special cases). But NDIS driver level. You 
need something like
WinPCap. Search on google and also look at Angus messages last week about his 
monitor component.

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