What upgrade can be done on an intel 845, P4 2.4 ??

hi,

i have an intel 845GVSR motherboard, running a 2.4ghz P4, with 256 mb single slot ddr1 ram. I have two HDD, one 80gig and one 40 gig, with a dvd-rom, and a cd-rw. The graphics and audio are on board, if anyone who has used this MB would know.

i use it for surfing, lots of downloading, limewire, bitcomet etc. and ripping DVD's and converting video and audio from one format to another.

I have the following upgrades in mind.

1) Ram addition increasing to min 512 MB. but should i add another 256, or single 512, or just go with 2 512 for 1 gig. i run xp pro. nero, various video convertors etc.

2) Should i replace the 40 gig HDD with another higher capacity drive, or just buy one of those laptop drives, which work via USB for storage? they are cheap and portable? will data transfer speeds suffer?

3) Install a DVD-RW in place of the CD-RW so i can store stuff onto dvd discs, but whats the min ram needed for that?

Any other upgrade please advise.