Aliens Abducted my Firefox??!!?!

I know this sounds crazy but a couple of weeks ago, my Mozilla Firefox stopped working on my desktop computer. I don't know why... I don't know what I did to make it go wacko...it just did. Basically it stopped working. My laptop was fine... no problem there, thankfully! I reverted back to Explorer, reluctantly, and limped along on my desktop. I stayed on the laptop most of the time, leaving the desktop to my son, home on break. Then today my home page changed and I asked my son why he changed it. He insisted he didn't touch it. Some site I never heard of was coming up as my home page...like using the explorer wasn't disorienting enough! So I thought I'd down load Firefox and try to fix it since now explorer was whacked out as well! It downloaded like lightening and pulled up my old home page and book marks instantly! I don't know how it did that... I just know that I'm grateful that it did! Finally, I can surf the net on the desktop and get to my bookmarks with out hassle!