Sql*Net not properly installed

[plSQLWannaB]

I am running plsqldeveloper on a windows xp virtual machine. (Created on a windows 7 box). When I start plsql developer on the virtual xp machine I type in a vallid Username/Password there are no Databases in the drop down list so I type in a valid database name then I get the following error: Sql*Net not properly installed OracleHomeKey:
OracleHomeDir:.

It appears to me that plsql developer cannot find the tnsnames.ora. It is this folder: C:\oracle\product\10.2.0\Client_2\NETWORK\ADMIN folder along with sqlnet.ora. I don't know what is wrong. Should tnsnames.ora and sqlnet.ora be placed in another folder? Please help with this urgent issue.

 

[Marco Kalter]

Can start PL/SQL Developer without connecting, go to Help > Support Info, and post the text from the Info page?

 

[zsmirnoff]

Do you use Oracle instant client? If you do - check this link:http://jasonvogel.blogspot.com/2007/10/oracle-instantclient-tnsping-and-plsql.html I do not encouridge you to follow this link though - I deleted oracle instant client and installed "regular" "fat" client...