How do I determine the cause of a very small table responding to queries slowly? I have a table that stores less than 3 registers, but the queries on it are very slow.

This table has only a single Primary Key with 0% fragmentation.

&gt; DBCC SHOWCONTIG scanning 'MYTABLE' table... TABLE level scan performed.
- Pages Scanned................................: 1
- Extents Scanned..............................: 1
- Extent Switches..............................: 0
- Avg. Pages per Extent........................: 1.0
- Scan Density [Best Count:Actual Count].......: 100.00% [1:1]
- Logical Scan Fragmentation ..................: 0.00%
- Extent Scan Fragmentation ...................: 0.00%
- Avg. Bytes Free per Page.....................: 7930.0
- Avg. Page Density (full).....................: 2.03%
If multiple threads are issuing the delete/update/select statements concurrently, then blocking is the most likely explanation.
You could use SQL Profiler and filter the trace on TextData Like '%MYTABLE%' to find all the statements accessing the table. 

https://stackoverflow.com/questions/4076516/how-to-profile-for-one-table-in-sql-server

However use caution with SQL Profiler in a production environment, it can impact overall server performance.