Iconia W700 so many problems

So over this thing.  It's nearly 3 years old, but most of the problems have been happening since very early on.  They've just got to the point now that they are so bad that I'm moved to seek answers.

The two things I'd love to get sorted out are:

1. Runs slow, sometimes effectively unusable, when plugged into the power supply.

2. Programs won't start up.

Details:

1. Firefox and Chrome become unusable when plugged into power supply.  Opera, on the few times that I have used it, doesn't seem to slow down.  Other software can slow down, as can the operating system / windows management.  Sometimes the whole system just grinds down to an unusable snail's pace with the fan going mental and not much else happening. 

I have a custom 'full power' setting that I set years ago once I discovered that "High Performance" isn't actually full power (WTF?!).  This problem is present no matter what power setting I have it on.  And not suprisingly it's worse on the lower power settings.

I've tried starting Chrome and Firefox in safe mode (all extensions disabled) but the problem persists.

I've cleaned their caches and temp files out (multiple methods) and do reasonably regular system cleanups with CCleaner.  None of this touches the problem.

2.  This is the one that drives me the maddest.  I can't pin down when and why this happens.  It seems to happen more straight after startup, but that's not always the case.  What happens is (on the metro interface) I touch the tile to start the program up, the tile deflects to show that it's been touched, and then one of three things happen.  It opens up as it should; the metro interface disappears (just the background remains) - this is the most common thing; or nothing happens at all.  When a program doesn't open like this, it either opens up anywhere between 10 to 30 seconds later, or it never opens up at all.  Lately I've noticed that when a program doesn't open and then I go to task manager (at any time point after waiting for the program to open) it opens up as soon the task manager appears (task manager ALWAYS opens up no problem).  This doesn't work for Firefox usuallly, though.  If I click say two or three times on the firefox tile over the period of say 10-20 seconds, and then go to task manager when nothing opens up, there will be three instances of firefox supposedly running.  The only way to get firefox to eventually run after this point is to kill all the firefox tasks and start again.  This usually, but not always, gets firefox running.  I should point out that Firefox is the most common thing I do on this tablet.  So it's problems are more noticable and I've investigated them more than other programs that won't start up.

This latter one seems to be getting worse.  I rarely use the tablet in normal desktop (non-metro) mode, so I can't be sure how often it occurs in that mode.

Any help on this would be appreciated.  This thing is fast becoming a brick.

EDIT: It's not a (known) virus.

EDIT2: I've got almost nothing superfluous starting up at start up.  In fact, I have the minimum services running as possible at all times.  There is the potential that this could be causing some of the problems, as I may have disabled a service that needs to be running.