1.ping your sever,be sure it is ok.
2.use oracle "SQL Net Easy Configration" setup your sever database.
3.setup BDE=>Configration=>configration=>drivers=>Native=>oracle
a. "Vendor init" must be collectly setup
b. Net Protocol "TCP/IP"
c. Server Name is the name u give the Database Alias's name at
step 2
4.if u finish the above,use the Tdatabase to test it
the important point is the "Vendor Init" setup,it is ora72.dll or ora73.dll,orant71.dll,U can select one of the first two to try.