Will my lenovo h430 take my Nvidia gts 250 graphics card?

Did you install the drivers? Is your monitor plugged into the graphics card, not the motherboard? Do you have at least a 450 watt power supply?

Yes it should. Make sure you have it in the correct PCI slot. I believe that card requires separate power from the psu. You will also need a 500w psu for it to work properly.

I've taken a look at the lenovo h430 and its case and you it should accommodate a NVidia GTS250, however this will also depend on the model. For example the XFX versions of the GTS250 are quite larger were as the popular zotac GTS250, s were smaller and would fit in almost any case ( except for small form factor cases )
i've also checked the specs of your Lenovo h430 and it appears it only comes with a 280w psu. This isn't powerful enough to safely run the GTS250, and you really should be looking at a 450w minimum psu with at least 1 x 6pin pci-express power connector ( although you can use the bundled molex to 6pin adapter that comes with each card )
a inexpensive and reliable psu that I recommend for the GTS250 is the "Corsair Builder Series CX 430W V2 '80 Plus Bronze' Power Supply "( http://www.overclockers.co.uk/...ubcat=1084 ) . This may be just 430w however being corsair this will be fine and its strong +12v rail and pci-e 6pin connectors make this a ideal choice for any GTS250 ( note: whatever you do don't run any GTS250 with a 280w psu. You card may work for a while but it will soon fail and the psu is put under too much stress )
so heres your checklist
1) ensure you have the required power supply. 450w or better ( or my recommendation )
2) make sure you have the 6pin pci-e power connected attached ( without this connected your pc will not boot )
3) ensure you have changed the settings in the bios. ( connect your monitor cable to the onboard graphics to access the bios ( that's the small blue vga port at the top part of the I/o plate area ) … Then you need to
a) change the setting "init display first " to pci-express or peg
b) if there's a option marked "onboard graphics " or "onboard video" make sure this is disabled
c) finally on the main bios screen make sure you press "save and exit set up" to save the changes you have made to the cmos (bios memory ) . Your pc will now restart and then wait for around 10 seconds and manually turn off the pc with the power button
d) now remove the monitor cable from the onboard vga port and connect to the GTS250…
now all going well and you should now see windows booting and your desktop should be clearly visisble…
this is a common problem and especially with oem systems from hp, compaq, acer and dell… These tend to have basic bios emproms which require you to change the video options manually…
I hope this has helped aaron. Any questions let me know