A few things that might help:
Right click My Computer, go to properties. Click the Advanced tab. Click the Settings button under Performance. Click the radio button next to "Adjust for best performance" and then scroll down and recheck "Use common tasks in folders." Click OK a few times to get back out.
Go to Start>Run and type msconfig and then click OK. Go to the tab that says Startup. Uncheck everything on the startup screen, then click OK. It will ask if you want to restart, so click Restart.
After you've done these two things, you will notice that not only does IWBTG run better, but so does everything else on your computer. One note though, is that if you clear out your startup screen, you won't have programs loading automatically when you start Windows, so if you have your IM client or something set to automatically run, and you want to keep it that way, leave it checked in the Startup screen. Of course, it's probably best to disable everything and then start programs manually as you need them.