I am afraid that you will be able to find the culprit

Please check if your tempDB is being shrunk too regularly? You may have to check auto shrink property of tempdb as well....

first you need to check the error message... kindly let us know what error you are getting....

Have you checked if your cluster services are running or not? worth checking that...

you need to freeze the cluster to do this task

Go to SQL Server Configuration Manager --> SQL Server Service --> Right click --> properties --> Advanced tab --> scroll down to version...

Just to add one point -->

You were seeing path as "C:\Program Files\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQL\Backup\ C:\SQLLogs_LS\dbname.trn" .....

The path C:\Program Files\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQL\Backup\ would have been the default backup path for your...

if you plan to make use of snapshot, do remember its static and will have data upto point in time when snapshot is created....

are you using Veritas cluster or Windows cluster? Make sure your R drive is a part of cluster and is available with the node you are trying to install...

In our environment we are not preferring this scenario and would rather request to opt out the mdf. ndf and ldf files as it have caused issues during DR exercise....

As a best practice and even you will find in almost all the SQL Server books, use the following naming convention:-

.mdf -> for primary data file

.ndf -> for subsequent secondary,...

Once installed you cannot change the instance name without doing uninstall and reinstall...

don't mess with registry.....

Possibly you have some custom job/script running on the server that you may have to look into...;-)

Well explained Lynn..... That is what exactly happening in these two queries...