Is there any limit on number of devices i can use with power supply

Honestly, odds are you are over-working your Power Supply, you can add a secondary power supply, they do make them for supporting Power Hungry video cards especially. If I had to guess you are also in a case without enough ventilation for your needs. I'd suggest getting a FULL ATX case, and at least a 650W PSU. You can do this for well under $200 at newegg. Also, it's best to give yourself about 25% headroom on your PSU, as running full bore will likely cause similar issues. The most I would suggest running on a 400W PSU is 6 drives, and that's ONLY IF you are running onboard video, and a reasonably light CPU and Chipset.

"There is a limit - each item you connect will have its own power needs. However, the amount required (particularly for processors and graphics cards) will vary very widely depending on what you have, so there's no easy way of saying how much you need without much more specifics on the hardware involved.
From personal experience, 400W is more than enough for most home users who only have one or two hard disks and CD drives. But a top graphics card or processor will devour that easily - many graphics cards recommend a minimum of 450W power supply on the PC. And the some quad-core intel chips can devour 300W by themselves at maximum load. A hard disk might take 15W, a CD drive possibly 25W. So already you've committed yourself to 145W without looking at the two most hungry components. Ditch at least 2 of the CD drives - 4 writers is excessive and I doubt will give you any boost over 2 because of other system bottlenecks."