These specs are for present only.
The more memory 512 ++ you have beyond a good Chip Pentium 4 (2.4 is norm now), the better it is.

The most important clue to your needs are to check on every software, what it requires, than understand this :
For example lets say your digital camera comes with a Photo Editing software that requires WinXP...
this means it will not run under Windows 98 ME etc. IT says something like this

Recommended 32 MB memory 16MB graphics card
Pentium3 800 MHZ or higher

Great you say , I surpass this by a lot .sure you do, but they did NOT tell you that this is the only program that is running and did they test this with Anti Virus Software running and a firewall Office open etc....can you get the picture? All these things running, require additional resources...

I am sure you have noticed that over time your PC becomes sluggish slows down etc.......this is where more is better HOWEVER nothing will safe you unless you get it cleaned up and that is where WE come in to optimize your working experience.
Internet Explorer needs something like 20++ MB's to run right alone, if you do any imaging, this skyrockets because while you work on an image, it stays in memory  ONLY when you save your changes does it get printed to the hard disk otherwise it keeps everything you do in temporary working memory, this is for example why they use JPEG which is about 1/10 of a Bitmap format. talking size here memory not width height etc.
The more icons you see next to your clock, the more resources are taken right of the boot up "starting PC"...and lots of them are not even visible there.
Now, if you do video editing or Drawing or AutoCAD alike, this gets SEVERE....any PC will crash if not correctly set up and hardware equipped, this is why they make super computers.