i have installed oracle 8i Enterprise Edition on Standalone system with Windows 2000 server OS.

System's cinfiguartion: AMD Athlon 64 x2 with 2.8 Ghz,
S-series Motherboard.

I want to install SAP 4.7EE on my PC,so i installed oracle 8i EE prior to SAP.
After complete installtion of oracle 8i,i want to check whether oracle is working or not.So i login to DB using SQL * Plus with userId:System/scott Passwd:manager/tiger and HostString.But iam getting error specifying with error code "TNS Protocol adapter error".
Before installing i have configured TCP/IP attributes using Microsoft Loopback Adapter.

I don't know what to do.
Could anybody help me regarding this issue.