Well, it is only 500va (watts) it isn't super powerful.
It can be used as a step up or step down transformer.
It has a 2:1 ratio in it so depending on if you are on the primary or secondary you will double, or half the voltage.
Do not put more than 100-125v on the coil rated 100-110 (X1 & X2?)
if you put 120v on the H1 & H2 side (200-220v) you will get about 60v

Add in a "Full Wave Diode Rectifier"
http://compare.ebay.com/like/1306887...Types&var=sbar

and you will have wicked pulsing 50 to 60vdc
add in some coils & caps & you can take the ripple out.

The problem with simple transformers is the rely on the magnetic fields collapsing from the AC waves to make it through the other end.
AC in AC out.

At 500w you might be able to get a magnetic rated house hold dimmer & roll the voltage down on the top side.
get it to 40v & you'll have about 10-12amps on tap

If you do get some PC supplies they could be paralleled or series'd (careful)... there are some tricks to doing that stuff...
PC supplies are sensitive to heavy startup loads & will shut down to protect them selves