Well if you have a robust back-up and recovery strategy then installing SP3 should be no real issue (which you should run before any major occurrence and installing an SP would fall under that heading).
-- SYSTEM BACK-UP & RECOVERY
If you fail to plan, then you plan to fail.
If you have a back-up and recovery plan, you can recover from anything in minutes, not hours or days.
1. back-up all the things that you don't want to lose, data files, like documents, spreadsheets, emails, email account details, registration keys, address book, favourites/bookmarks, downloaded files/programs, etc. the list goes on and on but if you don't want to lose it back it up. There are many back-up programs that can simplify this task and run it every day.
2. Recovery - re-installing your system really is a poor choice and one of last resort. There are tools (Drive Imaging software) that take exact images of your Partitions or Hard Disks and these images can be restored in minutes if you suffer a major catastrophe and that doesn't have to be a virus attack.
I do a weekly image of my partitions and save them to my 2nd hard disk, they can also be saved to off-line storage, DVD, USB external hard disk, etc. as part of my weekly system maintenance.
So if the worst comes to the worst at most I lose:
A. 6 days worth of program updates or new installations, but with my daily back-up I can recover most of that.
B. less than one days data files, emails, etc.
None of these is a problem and much quicker than a system reinstall and I don't have to go on-line to download the myriad of security updates needed to secure my system where there is a chance to get reinfected whilst my system has vulnerabilities because of these missing patches. Not to mention all my system tweaks and program settings are retained and I will have saved myself many hours of work and a huge amount of stress.
Many of these programs cost, there are some free ones, but it will take some research on your part to find these tools and decide on what is best for you from reviews, user feed back, etc. good luck.
