Lots of viruses try/attempt to exploit parts of the code around this area of windows operating systems.
Avast Antivirus home edition is an excellent anti-virus. Most of the reviews that discredit it (maybe all) must be paid for by the competition. I say that because I run virtual machines to test hacker ware on servers (keygens and hacked items that users post) and NOD and Avast are the ONLY consumer-based anti-viruses that consistenly CATCH or FIND the threats- kapersky sometimes. Norton and Mcafee almost never. AVG is decent as well- but Avast is the most "transparent" anti-virus we've found so far (transparent = runs without hogging system resources or slowing down the PC- so great for older or busy computer systems!) AND it is free.
For non-heuristic antivirus/detection I gamble all our network machines' first line of defense on Avast so far. AVG is 2nd choice. The pay-to-use ones just are not as good, hands down. I have Avast home on over 300 machines. Of course all traffic passes through linux based network with it's own protection, and all hosting is on linux hosts- which CAN find and catch all the problems.
NO ANTI-VIRUS, especially consumer based, is capable of detecting sophisticated hacker ware or code that it designed to exploit weaknesses in a system. Simply, it can not be done in windows; you can not completely protect a windows operating system. More than half the stuff we find and test is malignant and incredibly difficult to detect, though often it won't destroy something like the RPC in windows. The biggest problem with these "hidden viruses" is that they CHANGE the original code that windows uses, without discretion on what it might completely affect (why would they care?)- and windows OS's are like spiderwebs- change a few lines of system code and a week later your USB camera won't work and then you can't log into the net or find a printer. Go figure.
So the trick is, either
1) keep a handy ghost image and back your files up all the time (including MBR and partition tables)
2) Be prepared for problems down the road
3) Stay off the internet as much as possible- or only use ONE internet machine and keep it OFF the LAN!
4) switch OS's to something like the new consumer-accessible Ubuntu or SUSE- both rock and are so much like windows that within an hour you'll be back on the internet and DL viruses to your hearts content, without so much as a sneeze- immune to all of them, on an OS that's rock stable and just as good looking and easy to use now as windows, of any and ALL variants.
If you DO decide to check out either SUSE or Ubuntu, both are COMPLETELY FREE, as easy to install (easier) than windows (any) and can be DL over a fast internet connection within 20 minutes usually (1cd, depending) and you can install and TRY THEM OUT without commiting to having or using them or switching to them as your new os- if you DON'T like either, simply delete them or eject the CD!
Without looking I think the links and info are...
www.ubuntu.com
www.opensuse.com
Ubuntu 8.04 just came out- rock stable
openSUSE v11 the same.
RPC errors are common viruses and areas where windows gets broken- a symptom of "usage" of a operating system that is too fragile and simply little things get a little messed up, at best, in the registry.
If you have too many issues or problems with RPC errors, after 2-3 hours, simply reinstall or try a windows repair- any more time spent and not fixed and you're totally wasting your time- probably can NOT BE fixed without a reinstall!!!!!!!!!!!!!!!!!