Thanks for the response. I think the problem is with the graphic card on my comp. I tried paint weighting with a different computer and it worked fine. Thanks for helping me out. Graphic card on pc is,
Card name: ATI MOBILITY RADEON 9000 IGP
Manufacturer: ATI Technologies Inc.
Chip type: MOBILITY RADEON 9100 IGP AGP (0x5835)
DAC type: Internal DAC(400MHz)
Device Key: Enum\PCI\VEN_1002&DEV_5835&SUBSYS_FF021179&REV_00
Display Memory: 128.0 MB
Current Mode: 1280 x 800 (32 bit) (60Hz)
Monitor: Default Monitor
Monitor Max Res:
Driver Name: ati2dvag.dll
Driver Version: 6.14.0010.6444 (English)
DDI Version: 9 (or higher)
Driver Attributes: Final Retail
Driver Date/Size: 4/21/2004 23:11:38, 205824 bytes.

Which graphic card will work best for maya?