Server setup

I have a client that has a Windows Form .Net (1.1) application and an Informix database (IDS 9.4) running on the same server (dual PIII with 1 GB of RAM running Windows 2000). When large queries are run, the Informix server seems to crap out (never complete sending data) and about once a week the database service stops running and cannot be restarted. The message on the console is that the database stopped for an unknown reason and cannot be restarted. I am by no means a DBA, but I do have some experience with Oracle, DB2, MS SQL and PostgresSQL. The application inserts 12-18,000 rows a day into the main table. These come from a data file that is parsed (two large downloads a day, several smaller downloads). Items are grouped by various criteria (depending of plant floor location). Between shifts (about 1820), data older than 10 working days is deleted. I am wondering if the configuration for the server is correct. How do I find it? And how do I know if it is wrong? Before I changed the application to delete data, things got slower every day, until one day the server just would not respond. The main table has about 200,000 rows in it and it pretty much stays around that number. THanks for any pointers.