very low budget HTPC build, advice needed

[tech-wreck]

(as i'm new, quick intro)
hi, i'm andy, and i like to hack stuff. sometimes, it works 😀

anyway, i want to put together a HTPC, for basically £nothing. my tv and projector are both 720p, so i don't want to spend full HD money until after i get a new one.

i read somewhere (possibly on TH) that a socket 775 mobo is capable, if that's right then i'm halfway there. maybe.
i have an old dell optiplex gx620, with a pentium D 3Ghz in a 775 BTX mobo. i know it needs a GPU, some more RAM is already in the post.
i would guess the processor needs an upgrade, and the power supply too, it's only 250w or something.
the case is junk, as i will be putting it in a custom box, so no worries about large parts not being able to fit.

so, will the components i already have be suitable as a starting point? and what GPU will i require (i have a spare 9800gtx - would that do? ( i'll definitely need a new PSU to power that thing! ))
thanks in advance, all advice/suggestions will be gratefully received, even if it's "stop being tight and go buy something off the shelf" 😉
cheers
andy

ps, why does it keep popping up telling me to write properly? i can english!

 

[tiny voices]

The optiplex gx620 has a proprietary motherboard which will not fit in a standard case because it is not ATX, mATX, ITX.

 

[giantbucket]

Nearly any modern CPU (that has built-in graphics) can play 720p movies without needing a separate GPU.

If you really want a GPU, then something like a silent / fanless GT610 would be A-OK. Less than fifty quid.

 

[tech-wreck]

The optiplex gx620 has a proprietary motherboard which will not fit in a standard case because it is not ATX, mATX, ITX.

i'm sure i mentioned it was BTX. and it's not going in a standard case, i am custom building something. it will be made to fit. with flaming hammers if necessary.

Nearly any modern CPU (that has built-in graphics) can play 720p movies without needing a separate GPU.

If you really want a GPU, then something like a silent / fanless GT610 would be A-OK. Less than fifty quid.

i'm trying to re-use and re-purpose whenever possible, if i can use my existing hardware and only upgrade what is necessary, great. if i go down the modern CPU route, i'll also need a modern mobo to put it in, etc.
i think i need to get the tools out and do some hardware juggling. i will keep that fanless GT610 in mind, i'm sure i've seen them cheaper than that. i'll update when i've had a tinker
cheers
andy

 

[tech-wreck]

update:
1: the onboard graphics will play 720p content (streamed from youtube), good quality video but with noticeable and increasing audio lag. not sure if hardware or software causing that.
2: a 9800gtx will not fit unless i take a hacksaw to the serial connector/socket or the GPU bracket. i'm not that desperate. yet.
...
*goes shopping*