the past week i keep getting this error;

close programs to prevent information loss.

your computer is low on memory. Save your files and close these programs:

windows Live Messenger.

windows will only close enough programs to restore needed memory.

it has 2gb ram, and i put everything onto my external hardrive, so it cant be a space issue. dont know whats going on, but i just want a normal vista again.
i have the codes and that on a sticker on the bottom of my laptop for registration. can i download an install for vista and have it back to the way it was in the beggining?

a friend suggested to me to call acer and request a new disk for vista, but i dunno.

im running home premium if that helps.

thanks heaps.
If it's a relatively new Acer, then there should be a recovery disk creation software on there somewhere. Probably in the "empowering technology" folder. Burn the disks and boot from them. There might also be a bootable partition for doing a recovery, depends on the model, although most Acers don't have these. You could call Acer, as well, as they typically sell or give away these recovery DVD's.
1: There's a computer thread, use it.

2: Re-installing with the same programs won't solve anything. The system is clearly telling you it's out of memory, so 2 things could have gone wrong : either a part of your RAM is corrupted (really low chance) or you just have too much stuff opened. Just open the task manager and look at what's eating your RAM and close it.
Vista is a resource hog, it's a terrible OS, just download windows 7, it's still in beta but it's a lot better than vista, I'm running it since last year and I don't have any problems, just make sure that you download the latest version of the beta (build 7264)
getting the backup disks for it from acer would be the best option. otherwise you could torrent vista and just enter the serial number you have so it would be legit. of course you may just have a virus that is running a program to take up massive amounts of RAM. scan with antivirus first. i suggest avg if you dont already have it. if that doesn't work then reinstall vista with either of the ways i said and you should be rid of your problem
reinstalling vista... to FIX problems

sounds like a contradiction of terms to me.
Belief is a beautiful armour but makes for the heaviest sword.