PHP/MySQL difficulties on WindowsXP

Hello; We are having a miserable time with MySQL on a Windows/IIS server with PHP. Here's the version numbers: MySQL 3.23.58-nt PHP 4.35 Windows XP (although we previously experienced the same problems w/ Server 2000), 1gb RAM The site is for academics to submit scientific "papers" (data) for their organization. In addition to submitting data, they can browse and search the database. The problem is that one or more times per day, they whole thing grinds to a halt. Not sure that the server is completely locking up, but response times are so slow it might was well be. Restarting MySQL corrects the problem, but that may be a symptom rather than the disease. At one time we had IIS running on one server and MySQL on another. In this configuration, the IIS server would lock up, and reloading MySQL on *that* machine fixed the problem, according to my administrator. That server was remote, and the admin drove out to it to observe and noted that there were virtual RAM errors - running out - which motivated us to move it to the XP box in the office. There's really not much complicated going on here. The paper submission engine is session based, and some data is stuffed into session variables until it can be validated in later steps, then saved to the database. I've optimized the queries as much as possible, checked that MySQL connections are being closed and result resources freed, and php session variables unset and the session destroyed when appropriate. We're stuck, and the client is getting upset. Ideas? TIA Rob