Replacing my Mobo

you can put another micro atx with ease....maybe you ll need to change the psu and some connectors...thats all/

You can't replace the motherboard Dell (and other prebuilts) use proprietary parts, meaning you can't just swap out a major part and have it all work. Also, the OS is tied to the motherboard, so you would have to spend $100 for a new one (NOT AN UPGRADE VERSION).

Prebuilts (with the exception of the custom/gaming builders) have made it so about all you can do to upgrade the computer is slap new RAM in, replace the video card, and add a harddrive (if there's available space). The RAM isn't a sure thing, as you probably aren't told what speeds the board will accept.

Besides, the motherboard won't actually affect anything that you see. I would say that the motherboard has the least visible effect on performance, despite being the basis for the entier rest of the build. By the time you should upgrade your motherboard, you should be getting an entirely new computer. Which leads me to the main problem of your "upgrade": compared to what a $500 PC can get you today, your computer is a brick.

Celeron CPUs are anywhere from 6-10 years old, so the socket it drops into is almost as old as the dinosaurs. If your lucky, and I doubt it, the socket will be LGA755, which is almost 3 generations behind current tech. You can still build LGA775 computer, but it is highly recommended not to. DDR is also two generations behind. The lowest you can go nowdays is generally DDR2 800 mhz, which, once again, not recommended. The updated ones (DDR2) is just about dead, and the lower speed DDR3 is not being recommended except in extreme budget builds. New video cards are DDR5, none of which will work in the older boards.

Since you're asking about replacing a board you haven't been able to find for several years, I'd just go and call Dell about getting a new computer. Or spend a few of months learning about computer parts before even opening it up...

maybe only his mobo is dead and needs a replacement

In which case, all of my points about the proprietary nature of the part are still valid. Had it been a home build or custom built with a known motherboard, it would then be possible to replace the board. Still not practical though.

Regardless, it will be near impossible to find a replacement board, and tacking on the cost of an OS, it will only be a marginal amount more to buy a new prebuilt computer that is entirely better.

you are right...he will probably get a new mic atx from another company....costing £30 and a copy of windows £5. £35 in total....coz he does not want a core i7.

Wow. That's all kinds of wrong.

OP will need a board from Dell (the whole PROPRIETARY) part, which would likely be an arm and a leg. Windows will cost at least $100 (~70 pounds), unless you're buying a pirated copy. Which is illegal. A suitable replacement, if it can be found (which I doubt), will be probably more like another $100 (70 pounds), and will most likely not support the RAM and either not the DVD burner or the HDD (IDE vs. SATA). RAM will run another $70 for good sticks (50 pounds), and a good HDD (the better choice for an upgrade) would run $60 (40 pounds). All told: $330 (230 pounds).

For which the OP could get a new prebuilt which would be a lot faster.

To follow up on MadAdmiral's points:

The quick and dirty response is that if you're considering upgrading, and your motherboard is more than 2-3 years old, you're frequently better off just building/buying a new computer, as you are going to have to replace so much that it's rarely worth it, especially if it's a pre-built system.

My computer isn't that old, i when i got it i could have got a free upgrade to vista, but since everyone said vista was crappy i stuck with xp, and vista is only a couple years old. i think i got it in early 2007 or late 2006

Then you got screwed. Unless you paid $400.

Wouldn't "early 2007 or late 2006" be about 3 years ago? Unless my math is way worse than I thought?

At any rate, my comment was just a general rule of thumb, not a hard and fast "you must upgrade if X or Y". However, 3 years is a long time in computer years.

What do you use your computer for, anyway? If gaming, then you should expect to either rebuild every 2-3 years, or do some upgrades every year. If you just browse the web, email, do word processing, etc. then you don't need to upgrade nearly as often.

Can I ask why you want to upgrade your motherboard? What do you expect to get out of that upgrade? It's possible you could achieve the same goals with less intrusive or smaller upgrades.