Got an unusual reaction from Ken's computer when I tried to install the Actel FlashPro3 USB adapter. After first alerting me to a problem with the digital signing on the driver, it then cold refused to install the driver, with the message "This hardware will not be installed". This had the further unfortunate effect of locking out any other chance of installing the driver, although just for each particular USB port that I tried the adapter on (for some reason XP considers a USB adapter to be a new "installation" on each separate USB port. Fortunately for me this particular Dell had 6 USB ports built in. I was halfway through them when I began finding answers).
The short answer is that there's an option for driver signing checking that can be set to "Warn" or "Block", and it was set to "Block" on this particular computer. The best link that describes how to find and set the option was this one:
http://epsstore.ti.com/OA_HTML/csksxvm.jsp?JServSessionIdrootdlek21=sk38qb3i51.n6LzoN8L/AzOnMTOogTxpQOUtxCLbx0Ka0--&jttst0=6_23871%2C23871%2C-1%2C0%2C&jtfm0=&etfm1=&jfn=ZGC7722846B1965C3A173B60D74447730ADCDA2D62BAC770F48B94A4DECBA0B531D3DAFF87EFF42B47FC46FEF8672E4FC85C&lepopus=MCgMFTkEnGLWr9633c12WFtc:S&lepopus_pses=ZGD0C1329909761578899587F21F40759922FA043346DBC87B4924C179E1EA1A11B21140B68A8F1A07CC2FEB97090E0267F36BE8C149379E89&nSetId=91937&nBrowseCategoryId=10506&cskViewSolSourcePage=cskmbasicsrch.jsp%3FcategoryId%3D10506%26fRange%3Dnull%26fStartRow%3D0%26fSortBy%3D2%26fSortByOrder%3D1 (ugh.)
Furthermore, it is possible to force driver reinstallation for USB ports that are ignoring an attached adapter via the Device Manager. Just open the device manager and under USB ports find the "Unknown Device" (or the one with an exclaimation mark) and click on it to get a "Reinstall Drivers" option once the driver signing block has been removed.
http://support.microsoft.com/kb/314464
No answers found on how to blanket reset blocked devices on USB ports.
