Yes it's an oldie, but it still has its uses. Fortunately it is possible to install it in both Windows 7 32bit and 64bit OSes and Vista.
Installing this scanner in Windows 7 or Vista 32bit only requires using compatibility mode and administrator priviledges with the XP driver. Download the most recent XP driver (Twain 5 v 5.53) from one of the Epson websites, eg:
These drivers will install both Windows WIA support and Epson's TWAIN scanning interface.
Run the downloaded self-extracting .EXE file. As it extracts the contents to a new folder it will pause to allow you to confirm the folder's location (ie. c:\epson\...). At this point uncheck the box that says "When done unzipping run Setup.exe" and then click the Unzip button to continue. If you get a file/folder creation error while unzipping, run the EXE again with administrator priviledges. Next, browse to the Setup.exe file in the newly created Epson folder (eg. c:\epson\epson10245) and set the Compatibility options for Windows XP-SP2 and Run as Administrator. I happened to set these options for 'All Users' but that might not be necessary. Make sure that the scanner is NOT plugged in to the computer during the driver installation. Double-click the Setup file to install the scanner drivers and Twain. Reboot the computer.
Now plug in the scanner's USB cable and turn it on. When doing your test scans you'll find that certain applications (ie. MS Paint, Paint.NET and others) can only interface with the MS WIA scanner driver, which is very basic. The WIA driver also, apparently, does not recognise the scanner's TPU (transparency adapter) so it cannot be used for scanning slides or negatives. Epson Twain 5 OTOH works normally for both reflective and transparency scanning. XnView happens to be compatible with the Twain interface if you are in need of an app to test/scan using Epson Twain.
I've installed this driver in both Vista and Windows 7. When installed cleanly it works like a charm.
Now on to the Win7 64 bit drivers. This is a completely different situation and requires the use of modified (but still Epson based) drivers. Don't know who created the driver package... and I don't care cuz they work. ;-)
At this particular point in time the required driver can be found at either of these two links:
Download the file "epsonScan_1.0_Per1200Win64eu.zip" and un-zip it. Make sure that your scanner is not connected to the computer, then run Setup.exe. Reboot the computer, then plug in and turn on the scanner.
No compatibility settings were required when I installed it, YMMV on that. (A driver installation folder is created in c:\epson, similar to above.)
This installer puts "Epson Scan Ver. 2.68E" on the computer. It's been modified to include 64bit support for the Perfection 1200U and U-Photo scanners. I don't know if the Perfection 1200S (SCSI) is also supported. It includes a WIA driver, a TWAIN interface for use with twain compatible software and also a stand-alone scanning utility to scan directly to files. Note that the stand-alone Epson Scan utility will NOT run if the scanner is not turned on. This scanning interface isn't the identical to Epson Twain 5 but the functionality seems to be pretty much the same.
That's that. There are other methods for installing this scanner in Windows 7/Vista but these two at least conform to KISS.
If OTOH you're up to modifying installation files yourself there are some other installation methods discussed at the links below.