wow, how much did you spent to replace the whole computer? (if it's free, tell me where you got the computer
well, derived from your later paragraph, your using windows xp (you should say this up front).. and i have yet seen a "typical" bluescreen error in windows xp (can you tell me what exactly is written on the error screen?)..
one of the possible cause "might" be a memory problem, as graphical program makes intensive use of memory, you prob need to upgrade your RAM to 512mb - 1 GB?
service pack 2 is not "Bad", and it's mature enough (i hope) now to be installed as long as you keep updating
i wouldn't follow right up with a new service pack within 1 month of it's release though.. as it's usually make your computer worse, but after the month, alot of bugs have been fixed, then it may benefit your computer
mmm.. yes, windows firewall comes with service pack.. the firewall is pretty good for incoming packets, but i recommend you get a thirdparty firewall, as ubiquitous software is just too easy to be comprimised (mainly because of hte sheer number of people trying..), i don't see any preceiveble difference in speed when turned on