SQL Server process growing!!!

I have an SBS 2003 server running basically exchange, QB database manager and VPN access. The problem is the SQL server process is growing over 1 GB in size of physical memory in less than a week and seems to keep growing till server restart. I let it grow to 1732 MB last week in 9 days and it was growing as much as 200MB a day. There are some event errors in event viewer but I am struggling to find a starting point to fix the growing sql server. Can anyone give me a starting point or some advice?