Try implementing the fixes detailed in Clients performance  on this page. Although no-one is owning up to it, there does seem to be a well known (if not well documented), issue between the SMS Client and certain anti-virus software. TechNet article 228276 'SMS: Software Inventory Processing Degrades Foreground Performance on Win95 & Win98 Clients' also contains details on how to improve performance on Windows 95 clients.

If this is after the SP2 upgrade, in addition to installing DCOM 1.3, you must also install the WMI 1.5 (in that order).