PAE and more memory won't help at all. The problem is that you're running 32-bit SQL 2000.

Is upgrading to something released this decade on the cards?

If not, then you'll need...

User 2 will be blocked, as User1 will be holding exclusive locks on the table until the update is complete. User 2's select won't run until User 1 has completed...

https://blogs.msdn.microsoft.com/psssql/2015/06/10/operating-system-error-665-file-system-limitation-not-just-for-dbcc-anymore/

https://support.microsoft.com/en-us/kb/2002606

You don't need to understand the inner details of why the faster function is faster to use it. Just grab it from the end of the article and replace your...

Sure. Query sys.database_files (change database context to TempDB first) or sys.master_files and filter for database_id = 2

I'm not so sure. The average wait time is around 5ms for the SH, 1.5ms for...

Over what time period were those values accumulated?

Perfectly normal.

The binding order for columns within a subquery are:

1) Tables in the subquery

2) Tables in the outer query

Only if the column is not present in either will...

Open the SQL error log, find all the errors relating to that database, post them here. Do nothing else at this point.

CALs aren't monitored by SQL Server, but if you get audited...

25 CALs means you have max 25 people accessing that server. If you have more than that, and you get...

See my above reply for what you need to do in order to be able to get the information. For 5, I think you're going to need an extended event...

1) SELECT name from sys.procedures

2) SQL does not keep history of this information. You'll need to set up an extended events session to track this going forward

3) Short term history...

Performance tuning shouldn't be...

Traces are per-instance.

Start by identifying the queries/procedures which frequently get timeouts.