Ultra graphic card noob in need of help

Hi, I have a ATI Radeon 9200 series with 128mb video memory, it can play games like Call of Duty and Jedi Knight games easy, but I want to be able to play next gen games like assasins creed etc. I havent got a clue what kinda port it is or anything. Heres my specs.

HP Pavilion 061 DT033A-ABU t340.uk 0g`0211RE101XENO410
Windows XP Home Edition Service Pack 2 (build 2600)
2.60 gigahertz Intel Pentium 4
8 kilobyte primary memory cache
512 kilobyte secondary memory cache
768 Megabytes Installed Memory

Slot 'A0' has 512 MB
Slot 'A1' has 256 MB

RADEON 9200 SERIES [Display adapter]
RADEON 9200 SERIES - Secondary [Display adapter]
Samsung SyncMaster [Monitor] (17.1"vis, s/n H9NX900850, September 2004)
hopefull this will help. Can anyone help me?