Wrong forum section for your question.  This section is for Desktop AUDIO problems.

Repost on the Desktop General Hardware section and maybe someone will have an answer.  There is one important issue with some new Dell's and there are posts on the General Hardware section about that - some new Dell's require the higher priced "pure sine wave" UPS systems, not the less expensive models because of the type of power supply used in some new Dell models (both some XPS models and some of the commercial line models).  I don't recall which ones that is off hand but if you scan through the General Hardware posts for the last couple of weeks you should run across that.  You can also check the XPS Club section as that is just for XPS owners.

Also, keep in mind we are not Dell employees on here, just users helping users.

FWIW, my Belkin F6C100-UNV (5 years old with brand-new batteries) seems to be incompatible with the Studio XPS 435T. I spent $80 getting new batteries installed the week before my new Dell PC arrived. It powered my old Pentium 4 system like a champ, and had good UPS software (Bulldog). Oh well. Guess I need to spend MORE money.  

Thanks for the "pure sine wave" info. That will come in handy!

I found the following, doing a search, and it explains what is happening with many newer power supplies and why they need the "pure sine wave" (approx $500) UPS systems.

1. The PSUs in most new PCs, including Dell, have circuits to implement PFC (power factor correction) as part of compliance with Energy Star 4.0.

2. Power supplies with PFC can draw up to 1.25 times their nominal wattage rating during initial inrush. This can occur when the PC is first turned on, and also when mains current fails and any attached UPS switches to battery power. So, if you have a PSU rated at, say 470 Watts, you need a UPS able to deliver at least 587.5 Watts. This is true despite the fact that most PCs in normal operation draw a much lower wattage than the PSU rating.

3. PSUs with PFC are more sensitive than older models to the wave-form delivered by a UPS. So, they dislike the step-approximated sine wave of older/cheaper UPS models, including APC's Back-UPS series. Because of this, the UPS will try to use the battery constantly to make up for the problem. Which will make the UPS, in the long run, acquire several problems, like battery life time being shortened quicker than the 3-5 years.

4. APC's Smart-UPS series (models with an SUA-prefix) deliver pure sine wave output, which is what you require.

So: you need to find out the PSU wattage rating of, for example a Dell XPS730 (1000W), multiply by 1.25 (1,250W) and buy an APC Smart-UPS or similar from another manufacturer that can deliver a pure sinewave output of the appropriate wattage. The wattage output is not the same thing as the VA rating, which is what is mostly quoted in UPS model numbers.