OS: Win XP Home SP2 with all current MS updates.

Problem:  Digital cameras with SD flash cards connect and download pics.  HP PS 8150 printer connects and transfers pics from SD flash cards OK.  Both us the MS camera and scanner wizard.

However, a Lexar thumb drive and a SanDisk Sansa E250 mp3 player trigger a search for drivers.  The E250 connects and charges, that's all.  Both Lexar and SanDisk tell me I don't need drivers and that Windows should have whatever is needed.  SanDisk had me upgrade to Win Media Player 11, but no help.  MS won't talk to me because my Systemax PC came preloaded and Systemax support tried, for free even though the warranty's expired, but wasn't able to help.  

I found USB developer stuff on the MS sites, but no info about what I'm missing to use these devices.  They work fine on all my friends' and my wife's Win XP2 Home PCs and laptops.

I also checked the registry for an entry that PCWorld said disabled flash drives, but the entries they referenced are not in my registry to enable or disable.

Any ideas appreciated... Ed

It sounds like you are missing some drivers in Windows.  Reinstalling Windows to the same location may correct that.