I use both in my system, as well as ssd, so maybe I can help you out.
sata to ide adapters will require no f6 drivers when installing, but they are limited by the speed of the onboard controller. If you have ATA33 or ATA66, it can definitely be felt. Your i845 should have ATA100, so its not too bad. The adapters are usually cheap, too.
pci sata controllers will need drivers when installing the OS. They can be SATA300 or SATA150, but they are limited by the PCI bus, so theoretically they will max out at around ATA133 speeds: it really makes no difference which you use unless your motherboard has a PCI-X slot and your adapter is PCI-X. I prefer adaptec or promise chips, they have a bios though and depending on your motherboard you may have trouble booting with them.
Finally, if you plan on installing old windows versions with no official ssd support, I would keep a linux live cd or usb drive handy: you can boot into it and manually run trim every now and then to keep the drive healthy.
Personally I prefer the PCI sata controller, I think the only problem with it is the f6 drivers. If you have both a PCI sata controller and a sata to ide adapter, you can just use the latter to install windows, boot and install the drivers for your PCI sata controller, and then plug the drive into the PCI sata controller for a boost in speed and to avoid dealing with floppy drives.
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