monitor says no signal detected?

if you have on board graphics make sure you havnt plugged it into that slot.

does your computer sound like its booting up without you able to see whats going on onscreen?

take the side off your tower and push the graphics card in, maybe the guy didnt screw it in so its falling out of the slot.

Check the port is the correct one, by that I mean the big socket on the gfx card. If you have an onboard GFX card as well you will have more than one port in more than one place (The add on card and the on board which your PC might have had in the first place.)

Most modern gfx cards also have more than one port for multiple monitors. So check that as well.

The next more tricky bit is possible, especially if you have a card and on board gfx. The PC reads GFX from where it is told to go BIOS does that bit, which means it might not know about your GFX card yet so you need to consider BIOS settings.

BIOS, this tells your PC many things, one of which is what graphics card to pay attention to.

You will need to enter Bios. Turn it on and press "delete" when it says "press delete to enter setup."

Then look for a setting that says something like "AGP" or "Graphics". Usually under the advanced settings tab. (It all depends on which Bios you have as to where it is)

There will be a pull down menu if you have on board graphics and you should make sure it doesn't point to the onboard graphics. Saving the change afterwards.

Be careful BIOS is the critical bit of your PC, any mistakes should be exited without saving to be safe.

If unsure take it back and have him check it out.

You can download ccleaner for free here: http://bit.ly/1Bk5V5C

First open CCleaner

Go to the Cleaner tab and you will be confronted by a very confusing lineup of checkboxes.

To make this brief, below is my recommended setup:

Under internet explorer check temporary internet files, cookies, and last download location. Most users don't really need this stuff. keep history and bookmarks unchecked, history is a maybe, but you don't want to lose bookmarked sites. You can normally leave Windows Explorer, System, and Advanced alone.

Run CCleaner and it will start deleting files.

afterward it will present you with a list of the files deleted, you really don't need to go through it as it will be several pages long.

The registry cleaner is recommended for slightly more advanced users. Use it after uninstalling programs as they will often leave behind incorrect registry entries.

If you decide to run Registry cleaner then review the items detected and always back up the registry (I keep a folder aside for this)

The Tools tab lets you uninstall programs and set startup programs. Why do you need this if Windows has all of these features? Especially with Vista Home Ed. The windows defender software explorer( startup programs) doesn't pick up some entries (however software explorer is easier to use).

Using CCleaner to uninstall programs and then check for leftover registry entries takes less time.

Under Options you can determine how CCleaner cleans your files. I leave this alone.

It could be that the graphics card wasn't installed properly, it may just need reseating. Otherwise you may have conflict with the resolution settings of the card and the monitors you have tried. Ask the guy that fitted the card to sort it out..

have you pluged the monitor into the wrong port?

have you tried to shut everything down and restart ?

I had this problem ... take the monitor plug out of the computer and plug it into the next port along?

sounds like the cable from your monitor is stuffed,

Try making sure it is firmly seated at both ends.

Sorry, re-read your question _ I thought you tried your monitor on a different PC, not the other way around.

Peter (below) is correct with his answer.

sounds like a dogy graphics card

have you tried detecting a signal

how are you able to know your on the net lol