Try this:

control panel>display>effects>check the use large icon box>apply>ok.Go to desktop then go right back and uncheck the box. This resets ShellIconCache,

 if it doesn't work try this:

Go to my computer>tools on the top >folder options>view tab>check the circle beside show hidden files>apply>ok. Then go start>search>for files and folders>type ShellIconCache(capitalize S,I and C on ShellIconCache)>when it displays in the right pane>right click on it and when the properties box appears click delete>restart the computer. Windows will rebuild the ShellIconCache file.

Or download tweakui (microsofts tweaking software) and select "repair icons":

Tweakui for Windows 2000 can be found here:
http://www.microsoft.com/ntworkstation/downloads/PowerToys/Networking/NTTweakUI.asp

hope this helps!