while going through my add/remove programs to get rid of some junk, I noticed all three of the above-mentioned service packs...and they take up an inordinate amount of memory on my old Dell laptop (2.0 = 185MB, 3.0 = 170MB, and 3.5 another 28MB). Are they ALL necessary or am I able to remove any of them and still keep my computer safe?

I just went through all this Framework hassle. You need all the Frameworks because they build on top of each. 3.5 is an extension of 3.0 and 3.0 is of 2.0. If your comp. does not have one or you are missing one you will get loaded with spyware and malware even if you have anti software. That is what it did to mine. If you are low on space you could put your program setup files and programs that are not used often and move them to an external drive or a flash drive you can keep with you and plug it in when needed to run that program.