fixed my computer!
never did get a response from anyone viewing this website, but i realize people are busy. i'm posting here how it was resolved, in case it helps someone else down the road....
1. removed the hard drive from the "broken" computer and put it in a disk enclosure. ($60 at best buy)
2. plugged the disk enclosure into a working computer via a usb connection and backed up all our personal files (photos, etc.) onto that copmuter's hard drive and onto DVD.
3. tried to delete the damaged scesrv.dll file from the windows/system32 folder on the hard drive in the enclosure but the working computer would not let me delete the file.
4. tried to rename the file and then delete it, but that didn't work either.
5. tried to copy the same file from the hard drive on the working computer (both comuters are running WINDOWS XP) and paste it into the hard drive in the enclosure, but the computer would have none of that either.
6. put the hard drive back into the computer it came out of and turned the computer on. still had the error message (of course)
7. turned the "broken" computer on and pressed F2 to get into setup.
8. changed the boot sequence to boot from the cd drive then booted the computer from the cd drive with the operating system reinstallation disk inserted.
9. computer asked me to press any key to boot from the cd drive, so i did
10. a bunch of files were loaded from the cd and i was nervous that it would be reinstalling windows, but that's not what happened.
11. eventually got to a screen where i selected "1" as the system i wanted it to look at
12. pressed enter without typing anything first when it asked for a password.
13. at the command prompt, i typed chkdsk /p /r
14. took a REALLY long time to check the disk
15. finally finished and said it found one or more bad things. i was so hopeful that it repaired them.
16. but no, it didn't. when i took out the cd and changed the boot sequence back to the hard drive, the computer still gave the same error message about the file missing.
17. i found a link on a different thread on this board where the scesrv.dll file could be downloaded, so i used my good computer to download a copy. my computer had no problems with me moving that downloaded copy around from folder to folder, so i thought i'd give it another try.
18. took the "broken" ard drive out of its computer and put it back into the disk enclosure.
19. hooked it up to the good computer lo and behold, when i looked into the wndows/system32 folder there was no longer any file names scesrv.dll !!! i guessed chkdsk deleted the bad file, but did not reinstall a good copy of the file.
20. my lucky day. i pasted in the file which i'd downloaded, hooked everything back up where it belonged, and voila! could not believe how happy i was to see it all working again!!
THANKS EVERYONE who had posted on the various threads i read on this site. you all enabled me to piece together a solution. i hope this (sorry its long) description helps someone else someday. total cost of my repair was $60 for the disk enclosure, which i can see might come in handy in the future, and is WAY BETTER than giving best buy $200 or more for the repair.