Dell inspiron bios does not recognize samsung 840 ssd

Call DELL support?

Check all connections. Wiggle them a bit. Try again....

Can't wiggle much on it, it simply slides into the HD slot. DELL->out of warranty, calling costs 29 Euros...
Bios update ?
Is it dangerous to re-seat the drive while laptop is switched on ?

Don't mess with the drive when power is on. Just push it in and out a couple of times with power off. That's about the best you can do. Also check BIOS for IDE, ACHI, SATA settings and change some of them if possible.

Problem solved. DELL inspiron does not like SAMSUNG or the other way around. Called SAMSUNG, they are aware that the 840 SSD has an issue with Marvell controlers. I tried to find out if DELL has a Marvell controler on board, but the bios doesn't say anything about the disk controler. An upgrade of the bios might have solved the problem, but as I had no harddisk and didn't feel like making a boottable CD, I simply changed the SAMSUNG for an Intel 520 Series, 120 GB. (product code SSDSC2CW120A310).
It was about 50 Euros more expensive, but it works like a cream. Bios recognized drive, Win7-64 installed; and my son can continue on his essays..
By the way, this Inspirion already went through normal harddisks before this one -that's why I installed SSD. (the last one was a seagate Momentum, which should be more forgiving for "drops") There are quite some forums mentioning that some Dell inspirions eat harddisks...

I also have a Dell Inspirion (N5010 R15, chipset HM57) and I also want to buy samsung 840 but after your post I think it may be wrong decision. Colud you post more details about your dell model?

I recently worked on a DELL INSPIRON 1545 that was getting an upgrade to a Samsung 840 SSD. The other tech installed the SSD and had the same issue. No drive was visible in the BIOS and no amount of firmware updates or drivers was helping. After two hours I decided to try and help him out and had similar luck. Then I decided I should reseat the SSD. It felt like it came out to easy and upon further inspection and trying full size HDDs I realized the slimline Samsung 840 didn't sit in the caddie properly. The caddie doesn't screw into the business end of the drive, so it has the ability to sway up and down at the end of the caddie. After a little coercion, I was able to seat the drive into the SATA port properly and the drive became recognizable and we were able to install windows normally. When installing a Samsung SSD into a DELL Inspiron, always check to make sure the SATA plug is lining up properly and makes a satisfying 'ka'chunk' when it goes in.
TL;DR - Reseat your SSD and make sure the SATA port is pushed up to line up with the port. Try adding cushion above the drive if you can't get it lined up.