Yes, you should turn it back on. It is a vital piece of the operating system. If you need a performance boost, I would suggest an upgraded video card, more RAM, or a completely new computer.
The following information was found at this wiki page. The following is a quote from that page.
This service manages events and event
logs. It supports logging events,
querying events, subscribing to
events, archiving event logs, and
managing event metadata. It can
display events in both XML and plain
text format. Stopping this service may
compromise security and reliability of
the system.
I thought knowing the type of logs would be helpful to you, so I found this page. The following is a quote from that page.
Three types of logs are recorded:
Application, System, and Security. All
users can view Application and System
logs; only administrators can access
Security logs.
Application log
The Application log contains events logged by applications or
programs. For example, a database
program might record a file error in
the Application log. The program
developer decides which events to
record.
System log
The System log contains events logged by the Windows 2000 system
components. For example, the failure
of a driver or other system component
to load during startup is recorded in
the System log. The event types logged
by system components are predetermined
by Windows 2000.
Security log
The Security log can record security
events such as valid and invalid logon
attempts as well as events related to
resource use such as creating,
opening, or deleting files. An
administrator can specify what events
are recorded in the Security log.
If you need anymore help, let me know.