The "X" series of ATI cards should work just fine. I had an X1300, X1600 and an X1650 before my current video card and they all worked extremely well.
What I would do is go to ATI, here and download the latest driver (just the driver for now...not the whole catalyst control center which is the driver+the tuning software.
I ASSUME you have Windows XP, if not then go here and pick your operating system first:
http://ati.amd.com/support/driver.html
(I am going to assume you have XP Pro/Home, but if you have Vista, then fine too)
Click on XP Pro/Home in the left pane. Click on RADEON in the middle pane. Click on the right pane and scroll down to X1550. Click the green GO button and it will take you here:
http://game.amd.com/us-en/drivers_catalyst.aspx?p=xp/radeonx-xp
Go down to OPTION 2 and download JUST the driver only, which in this case is 14.7 MB to a temporary directory on your hard disk.
THen, I would go into control panel, system icon, hardware tab, device manager, display adapter, click on the "+" then click on the first listed device (there may be a secondary device driver). I would then go into the Driver Tab and then click on ROLL BACK DRIVER. It may warn you there will be no driver if you do this...do it anyway. If it does not say there will be no driver, there is then more than one driver (in the hardware database in the O/S), so do it AGAIN. The operating system will then make the Windows VGA stock driver the driver when you reboot.
Reboot the computer to reset things and allow XP to make the standard VGA driver default.
When fully booted into the desktop, go to the temp directory where you downloaded the driver and click on the EXE file and this will install the ATI X1550 driver you downloaded.
Reboot the computer again after installation to make the new driver default.
Right click on the desktop and then pick PROPERTIES from the menu, click on the SETTINGS TAB and set your display properties and click ok and you should be all set.
You can go back into control panel then and into device manager (follow my steps above, again), and double check that your driver has in fact been installed.
If you wish to install the full catalyst package, youcan now go back to ATI and download the full catalyst software which will allow you to tweak settings on the video card. You will have to download the driver and catalyst package, and catalyst will detect the current driver installed and only install the catalyst software.
You must also have DIRECTX 9.0C installed on you compute and you MUST HAVE Microsoft DOT.NET version 2.0 (check add remove software and scroll through the list to make sure you have NET version 2.0 installed)...if not, go to Microsoft and run the UPDATE wizard, and download/install NET version 2.0 OR HIGHER (current is NET version 3.5). The catalyst software WILL NOT WORK without .NET installed, version 2.0 or higher. This is one of the reasons why I did not suggest that you download the entire catalyst package because just installing the driver for the video card is not affected by the presence or absense of Net 2.0. We wanted to avoid any problems till you got a proper driver installation and then you can deal with the catalyst problems second.
I think this should take care of your problem for you.