same thing happened to me! I'm guessing you just installed Plus!, didn't you??
Disable speech recognition. For some reason, after installing Plus! and setting up voice command, WinXP turns on voice recognition, even after you've exited voice command. That service you mentioned was eating up 99% of my CPU, you wouldn't believe how slow my AthlonXP 1800+ was acting!!
I was able to turn it off by removing Voice Recognition as an available input method. To do that... uhh I'm actually at work right now so I'm not sure but I'll edit this post tonight at home. It's fairly simple to do (removing voice recognition), just go to Control Panel|Regional and Language Options, then get into your language input options, and remove it from the available input options list. I'll edit tonight with more detailed instructions if you can't find it in the meantime... Anyway once I did that, the voice recognition service stopped but the Plus! Voice Command still worked!
The other thing is, I still wanted to be able to use the mic for Plus! Voice Command, and I didn't want to have to enable/plug in/whatever the mic every time... By disabling Voice Recognition in Language Options, I was able to keep the mic active and still able to use Voice Command. Although, come to think of it, I recently set up Voice Recognition for Office XP Professional... works fine... or maybe I've reinstalled WinXP Pro since I had the proble...