Firstly, I would recommend that you start using an actual database. Anything, SQL Server, Oracle, MySQL, is going to handle larger data sets much better.
The sort of maintenance routine you need would not be exposed by normal SQL commands. The Access ide might have something but I haven't used it many years. If it's a one time effort, search the Microsoft forums. To do it all with SQL, I believe you would have to read with a select * and write that to a new db.
Consider a longer term solution for storing and archiving. At one location, I kept 3 months of complete test results and just pass/fail for the historic data. Using SQL Server, the database was at least as big as yours (several years worth) but I never saw any slowdowns. The schema was highly modified and extremely normalized from the default NI design.
