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[HippoNZ]

Depending on the age of the PC you could always do a defrag on the HDD. Also when the PC is running check what's using all the resources in task manager. If a lot of memory is in use either get more ram or increase the page file size. You can always image/ghost your hdd but make sure you don't do a sector by sector copy, that way you can reformat the drive and chuck the image back on it and it will be the closest thing to a rebuild you will get without actually starting from scratch. Also check to see if you have any background programs that are using a fair amount of CPU, if there are google them and see if you can remove them without any side effects. If it turns out to be the OS at fault it can be hard to determine whats causing it to run slow and is generally just easier to wipe and reload. As for the USB/serial, I know the problem your having as we had the same issue at work but try experiencing with different drivers and hopefully you should find one that will do the trick but in my experience they can be rather flackey to work with.