presently i m using oracle 10gr2 client on windows XP & oracle net configuration Assistants & net manager are not open properly.
Here is any way to repair oracle client or uninstall client and reinstall again
You don't necessarily need net config assistant or net manager to run as all they do is generate text files (tnsnames.ora and sqlnet.ora) for you.
If you have a tnsnames.ora file and sqlnet.ora file from a different installation you can probably just copy/paste them into your %Oracle%\network\admin folder and see if that gets you going.
To remove the Oracle software and restore the machine to a 'clean' state if you want to retry the installation is a bit of a hassle because it involves manually cleaning out the registry, your PATH environment variable, etc. However, if you have access to My Oracle Support, the following note walks you through it: Note 124506.1 How to Remove the Oracle Client Software Before Reinstalling