I wont say good enough, but you can run Vista Ultimate on that system. Well you may not be able to get Aero interface etc. But you can run Vista Ultimate.
Check the minimum system requirement for Vista here.
Which says: Windows Vista minimum supported system requirements
Home Basic / Home Premium / Business / Ultimate
800 MHz processor and 512 MB of system memory
20 GB hard drive with at least 15 GB of available space
Support for Super VGA graphics
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I have been running WIndows Vista Ultimate since the days of Beta to present Vista SP1 on one of system , AMD Athlon 2000 XP, ie ~1.7GHz, 512 MB RAM of which 32MB taken by In-built video , so effectively 480 MB RAM. It works well but yes a bit slow no aero, no eye candy.
So your system is much better than mine, So it'll run, get correct drivers. If you are having Vist, install and check . later on you can increase RAM if you want but yes you may not be getting all the PLUS of Ultimate as aero interface etc.