Question : Problem: CPU usage = 90+%--upgrade time?

My AMD Athlon 2100 seems increasingly to be in a high state of usage.  For example, importing a music CD into iTunes will take 100%; Firefox will take 40% when Pandora radio feed is open; Outlook 2007 is slow to reveal html emails.

Is it time to upgrade?  I'm thinking Intel duo core is appropriate.

I do no gaming; typically have open Firefox, Word and Powerpoint and only the essential startup items.  

Answer : Problem: CPU usage = 90+%--upgrade time?

i would suggest cleaning out the system a bit :
-delete all old / unused files from my documents
-uninstall all not needed software from add /remove programs
-run all these to remove malware :
     adaware :      http://www.lavasoftusa.com/
     Spybot :        http://www.download.com/3000-8022-10122137.html
http://housecall.trendmicro.com/                                                               online scan for trojans
http://www.spychecker.com/program/hijackthis.html                                   download
http://www.hijackthis.de/index.php?langselect=english                                check the log

run a disk scan for errors on the disk : right click disk>properties>tools
if it comes back clean, you can also run a defragmentation on it, from the same tab

a faster solution is a complete backup, and fresh install (i do it every year at least !)