Mohit
If the Microsoft uninstaller utility didn't work we would advise you to open a normal support issue as we will most likely have to do a remote session. but if you are sure the uninstall worked and you are now receiving a 1603 errors most likely that is a permissions error
verify the following
1. the account you are logged into Windows with is a member of the local administrators group on SQL server. Do not use inheritance from a group like Domain Admins, make sure its explicitly listed under the local administrators group .
2. make sure that Windows account also has the SQl Server Role of SYSADMIN explicitly assigned to it.
3. If an upgrade or shared MDB make sure all CA Services are disconnected, so stop caf and all DSM Explorer machines before running setup.exe.
4. Make sure you are using a good copy of the install media and that you are copying the install media locally to avoid corruption and network issues.
5. verify the SQL information you are entering in the setup wizard is correct
verify port and instance name are valid and can be connected to via SQL Studio Manager.
If the above is verified and you are still getting the 1603 error you would need to examine the logs that get generated in the %TEMP% directory specifically the following logs
DSMSetup.log
TRC_Inst2_ITRM.log
TRC_INST_ITRM_#.log
depending on how far the install got before it failed also check
\CA\DSM\database\setup.log
\CA\DSM\database\mdb_install\install_mdb.log
\CA\DSM\database\mdb_install\install_mdb_msg.log
If you open a regular support issue to save time attach the entire %TEMP% directory and the files mentioned in the \CA\DSM paths so an Engineer can determine what is causing the failure.
I hope this is helpful
Joe