You need to pay attention, ClickRight. This is a different machine than the first instance and it has not reset to PIO...at this point the HDD appears to be fine. The HDTune (free version) you suggest will check far less than the free utility from his HDD manufacturer's website.
Some additional cleanup may be needed and, perhaps, some additional RAM, but we won't know that until MahatmaGandi replies with the information.
Just read the thread over again, and it appears MahatmaGandi machine reverted to PIO mode as well. My reason for checking with HDTune is to get an idea of the SMART values of the drive (for example, reallocated or pending sectors.) This may give us some insight to his computer's slowness. It would not be a good idea to run certain manufacturer's tests on a drive that is approaching it's limit of bad sectors. However, if the SMART values are OK, it may be a good idea to run the manufacturer's test, but only after a backup has been done of the data.