sqlservr.exe suddenly consuming more memory

hi all…

environment:
Windows server 2003 sp2
RAM 4GB
Sql Server 2000 sp4
single instance
only one database
four jobs are running there.
installed 2yrs back and running cool,suddenly the sqlservr.exe consuming nearly 3gb. previously it was below 1gb.
i’m not able to get what exatly the problem.
please some one help me.