Windows uses a 'shotgun' approach with hardware drivers. One of the reasons Linux (on the desktop) is finally getting popular is because the Linux devs are doing the same thing as Windows devs. As a result, the Linux kernel is becoming Windows-like, e.g. fat and bloated. But, that's okay, because it's letting n00bs get their foot in the door, you know? Besides, the processing power of computers is doubling every year, so bloat really isn't an issue these days - except on older machines.
The thing is...
After a while, you're going to start realizing that (say) your display is flickering when you're watching videos, or playing Flash games online - because your lappy is using generic Mesa drivers, or whatever. You're inclination will be to blame it on Linux, but the fact of the matter is, it's because YOU haven't compiled custom drivers for YOUR hardware.
The 'fix' is to compile a custom display driver set, specifically made for your machine!
Ummmm.... what?
The kernel isn't getting fat and bloated to my knowledge . Video drivers were moved into Kernel-Space memory wise, but other than that I don't have any clue what you are talking about...
There should be absolutely no reason to compile your drivers from source. Sure you MAY get better results if you apply very specific optimizations unique to your system during compilation, but other than that, once again.... what are you talking about?
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OP, given the system specs, you probably want to stay away from a KDE base Desktop - it typically demands the most memory and processor cycles.
XFCE or Gnome will be your best bet.
As for the LiveCD not working with suspend-- thats typically just a bad idea in general. I would install Ubuntu 9.04 and grab all the available updates. I assume you are running Intel based graphics on that Dell - thus enabling the Xorg-Edgers repo as well as installing the latest Kernel will be highly beneficial.
I would imagine that power
management if configured properly is worlds ahead of Windows XP. Honestly, XP should not be the bench mark - its 6 years old for crying out loud.
Undervolting is unnecessary in my opinion. Recent OS's and processors do a well enough job managing their sleep states as it is. Further undervolting - especially on a laptop - just isn't wise.
Windows XP, given that it is, BY FAR, the oldest of the 3 OS's will, of course, be the snappiest. If you're going by that though, you might as well install Windows 3.1 .
Honestly, I would stay away from XP like the plague for many reasons.
OpenSUSE is a very nicely put together OS; however, I found that the package manager and repositories are immature. Often times to get anywhere (MP3 codecs for instance) you have to compile and run from source (Perhaps this has changed since I last used it). While this gives a pretty cool look at how an OS works, it can be tedious. Additionally, as I said earlier, KDE tends to be sluggish compred to the other counterparts.
Ubuntu 9.04 out of the box (on Intel and ATI graphics hardware) is quite a horrid mess. It honestly should not have been released the way it was!
That said, after you apply the most recent kernel and updates, 9.04 is quite possibly one of the best Linux distros I have ever used. Everything just plain works! Even on my 64bit machine with 4GB of RAM, I am only using ~11% of my available memory (Very remarkable for a 64bit OS).
On my Core 2 Duo based T61 laptop I typically draw around 18-19 Watts average.
-Kevin