I go with Lady Lee.....do a good clean up!! And clean out your temp files, cookies, all that junk, and then scan disk, defrag.
I do it all once, maybe twice a week as I play with huge graphics files....the more you do it, the shorter time it takes.
Also, if you are on "Dial up Modem", when it goes from "peak user time" to "off-peak user time", your PC may suddenly be operating at a higher speed.
Do you notice this when you are just sitting quietly reading a post? Not surfing around? If so, it's a sudden rev up of received data.
Just my opinion
Ana