What operating system are you using? Have you manually gone to Windows Update to ensure you have even the non-critical updates?
Have you ensured you have at least 20-30 gigs of free, clean freshly defragmented space on your C drive? Are you editing your video to a second or hard drive? If so, have you ensured this drive is formatted NTFS and not FAT32 (as they come from the factory)?
When did you last run a cleaner/registry tuner on your system? The terrific free program Advanced System Care will tune up your whole system with just a couple button clicks. http://www.iobit.com/advancedsystemcareper.html
I run it every week, and my six year old computer still runs flawlessly.
Finally, if the program is crashing while you're editing video, what kind of camcorder is this video coming from?Have ensured that your Vegas project matches this camcorder's video specs?