You mentioned talking to 'tech' support, did they say anything about tweaking Windows and have you done all of the standard Pro Tools LE tweaks, Do you have Antivirus, or defragmention software running in the background, that should be disabled ... and even though all your equipment is Digi approved, you could still have it configuired poorly for Pro Tools use. I would check my XP tweaks and go from there, like make sure you are using the porper version with the correct pacthes installed, like 6.9 and SP2, or 6.4 or .7 with SP1, Are your USB ports turned off, how about the printer/serial/com ports that you are not using or is the on board sound card disabled, are you hard drives properly formatted and set-up ... are you using SATA or IDE drives. Some Tweaking resources are
www.musicxp.net and
www.blackviper.com ... and of course Digidesign.