Was this laptop repaired by Dell ?

No i had repaired it from laptop repairing shop.

Can u tell me what problem it could be?

They probably replaced the system board during the repair.  Most Vostro models are just Inspirons with a different paint color outside - the boards are very often identical.

I doubt Dell will have any updated drivers for a system that's now approaching a decade old.  Use whatever drivers are available for whatever the 3550 supports - or the Inspiron equivalent board the system now contains.  

So what u suggest for maintaing my laptops for drivers and other thing plz suggest me

Should i use inspiron drivers.Is it safe for my laptop?

If it's working now, leave it as is - there's no problem. 

@931997 

For all intents and purposes you have an Inspiron because the motherboard is the most important component of your laptop.

If you want to update the BIOS you can, but I would not if everything is working fine.

.

I had a similar problem. I dropped coffee on my Vostro 3560 and needed to replace the motherboard LA-8241P model. That's the same motherboard model for the Inspiron 5520 and 7520. That's why I received a motherboard with a Inspiron 5520 BIOS wich not recognized all my devices, including the off-board graphic card AMD Radeon 7670M. I have a little knowledgement about eletronic circuits and looked in the internet for the LA-8241P schematics and the Vostro 3560 BIOS .bin files. The BIOS in this motherboard is writed in two memories, UH2 and UH6 (schematics names) or 25Q16 and 25Q32 chips. I found the .bin files in online foruns, downloaded it and writed the .bin in the chips with a CH341A USB programmer. After, I replaced the chips on the motherboard and voilà! I have my Vostro 3560 with all resources able!

It's possible to found the UH2 and UH6 chips writed for the Vostro 3560 BIOS for sale at the internet too. In this case you or a technician need to replace it on the motherboard.

Sorry for my bad english. It's not my native language. But I hope I helped.