Memory leak tracker

Is anyone aware of software capable of logging (in Windows 98) what applications/drivers are not releasing memory? The situation is that we have custom written VB server-based application which runs 10 production lines, each of which drive three printers, one scanner, one touch-screen monitor, ups software, dual parallel port card, video, NIC, and wincomm 8 port serial card. With 128 mb of physical memory installed, I am using approximately 85 mb after starting the application. Within 20 minutes all physical memory is used up. The software vendor wants to charge us to find the leak and doesn't think that it is their application.
Thanks