hey jhonny how's the girls chasing going on...
well sorry to say but plz dump ur celeron and ur current motherboard and ram....
now u want to have a sys. within 20K to let u play latest games like doom3 and HL2....well lets try...
processor: AMD Athlon 64 2800+ priced arnd. Rs.5300 approx.
Motherboard: Asus K8N(nforce 3 chipset) priced arnd. Rs.5500 approx.
RAM: Transcend 256 MB 400 Mhz priced arnd. Rs.1600 approx.
Graphics Card: ATI Radeon 9600 SE, 128 MB DDR priced arnd. Rs.5500 approx.
Total Amount: Rs.17900 or max Rs.18000
Rest assured that with this config. u'll be able to play latest games at MEDIUM SETTINGS....
EDIT: If u get this config. within Rs.17000 then try to go for Radeon 9600 pro instead of 9600 SE...its just 3K more then Radeon 9600 SE but better in performance...infact i suggest u to go for radeon 9600 pro if u can..
gud luck!
ENjoy