You need an interface that is better at low latencies-

Lance

Try changing 128 and 44 to 512 and 44 and see if the popping and clicking comes to a stop. Sounds like your computer chip is trying to do all the work up front to output a signal... increasing to 512 my eliminate the problem.

I'm shooting from the hip on this one... your computer is spec'd just fine. But from experience, I know that HP puts so much bloatware on their computers, and even worse, programs that garbage to start at startup. ///

CLICK through this process, START > ACCESSORIES > RUN.
When the dialog box pops up, type: msconfig
When the next dialog box comes up, look for STARTUP tab... UNCHECK EVERYTHING... If it's in that startup tab, you don't NEED it, whatever is there will start when you start a program that actually needs it.

You are not done - click APPLY... let your system restart... Once your system restarts (of which it should start WAAAAAAY faster), try to record something at the highest settings for the MobilePRE... 512 at 44 then start backing off.   Also, I'm assuming you are not scoring music for a DVD release at this point, so back off the bit-depth from 24 bit to 16 bit. 

If you don't see any noticeable change, either in startup time or recording, try going through the above steps again EXCEPT go to the SERVICES TAB... at the bottom is a box that can be checked that says HIDE ALL MICROSOFT SERVICES... CHECK THAT BOX the choices above that box will change... GO THROUGH AND UNCHECK everything that is left... Chances are this will knock out your ANTIVIRUS as well...stay offline until you run a check...

When your system restarts... go through your checks at the highest levels and work backwards. If you are worried that you unchecked something important, you can always go back and reset that item. If doing all this helps, then your dealing with a computer that had a bunch of crap installed in it. At some point you may come across a setting or a program that re-initializes some of this stuff that you just turned off, as a suggestion, SAVE EVERYTHING that you want to save and REINSTALL Windows 7 ONLY... then put SONAR on it.. then your Maudio drivers then run through your tests... when u are satisfied with what you've got, be extremely selective about what you install on your production system.

yes... the read/write speed on an external drive is usually a time killer, especially compared to a 7200 rpm internal SATA hard drive. there again, I didn't even think of that... your internal hard drive may be a 5400 rpm hard drive... that can be a bit of a kill.  Do a google search on "turning of unnecessary services WINDOWS 7."  Some of the tech sites go into better explanation of the "background" services that you can turn off and still have a viable computer.  That will open up the resources on your system for music processing.

Another slow down is ON-BOARD graphics, the higher end graphics card you can provide the more resources you remove from the CPU.  That doesn't mean you need a $700 card, but a budget card vs a quality card can help improve performance, pinpointing everything that can be wrong is time consuming, but x1 is supposed to be able to run on a two core PENTIUM 4 or better, and a PHENOM 6 core with 8 gigs of memory should scream.