Hmm - well Windows Movie Maker is far from the best program to make vids in.
It is however the cheapest since it comes bundled with Windows XP.
If you want to get a bit more serious about your vids then I recommend using programs such as Adobe Premiere, Sony Vegas, Adobe After Effects or Ulead.
If you do decide to get one of those programs then I suggest buying 2nd hand. Adobe products brand new tend to cost an arm, a leg and often a soul or two
