Replace a Motherboard with OEM Vista?

I have recently been thinking of replacing my Asus IPIBL-LB motherboard in my HP m9200t as a first step in doing further upgrades to my computer, but i am a little confused about part of the process, specifically what to do after the motherboards have been swapped.

I read that in some cases you have to use your boot disc, but obviously i don't have one. Since i really don't want to buy a new copy of vista, will a mobo of the same manufacturer secure that i don't have to buy a new copy of vista? Like replacing my Asus IPIBL-LB with a ASUS P5Q Deluxe LGA 775 Intel P45 or ASUS P5Q LGA 775 Intel P45 ATX? And If those would also require a boot disc, could you please advise me to some mobos for a Q6700 that can use 1066mhz or 1200mhz ram that wouldn't?

Any help would be greatly appreciated.

Your copy of vista is proprietary with hp boards only, if it's anything like my compaq pc (which had an hp board). I used a dell oem vista cd to reinstall vista, and had no problems activating it online using my vista coa sticker number. I didn't even have to call microsoft. Dell oem cd's for vista or windows xp are available online at places like 9software or under the header "operating system" in pricewatch. Around $17, last time I checked.

i know your pc is an hp, but im replacing the mobo in my dell on friday and had the same question. i contacted dell and asked could i use the oem disk that came with my pc on the new mobo and they said as long as i have the product key i could install the oem software on the new mobo. so if you have a product key sticker on your pc case, from what dell told me (2 times, i wanted to be sure) you can change the mobo as many times as needed and use the oem software as long as you have the product key.