Robin, Sergey answered your other question (about whether SQL SELECT statements outside a BEGIN TRANSACTION are affected by any SET ISOLATION commands), though I don't necessarily agree with his response about accounting reports.

Here's an easy way to test - open two SQL windows and issue queries and UPDATE statements against a single row in a table, and set your transaction levels accordingly. It's a quick and easy way to test behavior. Any SQL training class that covers isolation levels will use that technique.

Kevin