well it depends of a lot of thing including the Hard Drive, if you have your hard drive full of programs and games and whatever, then it will take more time to load each thing because it works like this:
100 mb for firefox. 10 mb here, he other 50 mb there, the other 40 near the 10.
It will take time to load each thing from a different place of your hard drive partitions.
If you do defragmentation, it will help you to make it bit faster, but, a hard drive format would be better.