Post your http.conf LESS the comments.
Be sure to check your setting for KeepAliveTimeout
Setting this to 1 can make a big difference in reducing server load.
These settings also affect server load:
Be sure to restart Apache if you make any changes to http.conf.
Also, as Falko suggested, a good php accelerator can make a big difference if your website contains lots pf php. I use XCache and find it to be better than eAccelerator but YMMV.