I don't know if I'm correct, but the SB Extigy does not have ASIO drivers. This is an External USB Soundcard.
If you have other USB peripherals connected to your PC/Laptop you might want to disconnect them when using the SB Extigy. The Extigy works on USB 1.0 and it does not have the bandwidth capacity to accomodate the SB Extigy and other USB peripheral at the same time.
I don't know if you have the latest update to the software, but there is an update available to help aleviate some of the latency issues. However, it does not fix the USB bandwidth problem just some software issues.
http://us.creative.com//support/downloads/download.asp
Here is a list of the fixes and added features:
Fixes
Cakewalk SONAR 1.3.1 (Trial Version) detection of Sound Blaster Extigy as monaural device
Wave Volume level changing to the default level after forwarding, rewinding or muting the track in Audio
Mixer while playing back AC3 files.
EAX On/Off button in PlayCenter responds correctly to remote control
Fader and Center speaker volume in Audio Mixer is accessible after headphones are disconnected.
Updating drivers in Windows XP no longer requires a system restart.
Speaker configuration setting is saved after the restart.
Improved 3D audio processing.
Added Features
Enabled compressed AC3 pass-through for output to an external decoder.
Added Bass Management Configuration
Sample Rate Conversion engine has been improved to allow playback of 24bit/96KHz files through the 16bit/48KHz engine.
Added Firmware version information in the Audio Control.
Added DirectSound Voice Management in WinXP.
Firmware V 1.1.020507
Added AC3 pass-through
Added Bass Management Configuration
Improved CMSS playback quality.
Improved device recognition on system startup.