Is it possible to add a second drive to X60t? I understand that it's rather small, but it has a second (empty) mini pci slot and expresscard slot.

Can I install SSD disk or CF via adaptor and into one those slots? If yes, will I be able to boot from it?

You have several options:

1. 2.5 inch hard drive / SSD via Ultrabay Adapter + Ultrabase. Granted, this isn't exactly "internal", but it's the easiest and least hackish. Bootable. Speed slightly limited by the Ultrabay's PATA interface, but still likely the fastest among these options.

2.1. MR15 + micro SD cards or MR04 + SD card in second mini PCIe slot, or
2.2. PM3U + USB drive in second mini PCIe slot. Both 2.1 and 2.2 uses the USB lanes in the second mini PCIe slot, and appear to the system as USB drives. Note that the second mini PCIe slot only has USB lanes, so you cannot use any real PCIe cards or mSATA SSDs in it. Might be bootable as USB drives, but you certainly cannot install any Windows systems on it easily.

3. SD card in SD reader. It is sllllllllllllllllllllllllow. Not bootable.

4. CF card + PC card adapter in PC card slot. 16 bit adapters are slllllllllllllllllllllllllllow and only supports small cards. 32 bit adapters are impossible to find. Not bootable.

thanks.

seems there's no good options

twistero, those all sound like good options to me! offhand, is there more info on this board relating to those options? I searched using "PM3U", "MR04", and "MR15" with few results- just the info that one needs the whitelist-removed BIOS.

have you personal experience with one or more of these adapter cards? the sales website claims that the MR04 "can’t bootable to Windows XP/Vista" but interestingly the MR15 "can’t bootable to Windows XP/ VISTA / Windows 7 " ... so possibly the MR04 CAN bootable to Windows 7, (so to speak0?

Any further information appreciated!

No, I don't have personal experience with any of these cards.
Regarding Windows installations: both MR04 and MR15 are USB devices, and in general you can't install a full Windows system to a USB drive or any other removable media, at least without some serious tricks. Google for more info.