Whenever I start up my comp., the first thing that pops up is "blfjfubyin.exe is not a valid Win32 application".. any ideas on how to fix this problem?!

Interesting. A google search yielded nothing on that file name. Are you certain of that name? Check your msconfig and see if it appears there. Start/run/msconfig startup tab. If it does, uncheck it. Make a note of the path also and go looking for it and try to identify what it is and what it will take to remove it. (assuming it isn't something you need)

You may have a virus or trojan or worm or adware or some other sort of malware. Run an AV scan, and download AdAware and Spybot, install them, update them, and run. Delete anything that looks suspicious. Some advise deleting everything because it's all reversible. Also get Spyblaster which keeps a list of bad stuff on your computer and blocks them from being installed (theoretically). Be sure your independent (not MS’s) firewall is enabled. If you had in mind running Hijack This as well, and posting your log, don’t until after you’ve run the two programs below. If you don’t do this, the forum moderator will delete your post. Then if you want to run HJT and post the log, suggest you do so in the Security and Virus settings and say you’ve run these two already. Spybot AdAware