I just bought a new sata samsung 250g hdd but my pc is not picking it up only my ide hdd i'm running windows xp and my m/b does support sata. what must i do? please help
If your motherboard doesn't support SATA, and if you have a free PCI slot, you could add a SATA controller. These are relatively low cost and typically would support 2 SATA drives. You might also need a simple Molex to SATA power adapter if your power supply doesn't have SATA power connectors, and a SATA data cable. (or you could go back to the place that sold you the SATA drive and have it replaced for an IDE one....)
When you say, "but my pc is not picking it up", how do you know that? IF you installed a brand new HDD and went looking for it right away in My Computer, you will NOT find it there! Any new empty HDD has to have two operations done before an OS can use it. You must Create a Partition on it, and then Format that Partition to install its File System. some people refer to these two steps together as "initializing the drive".
To do this you can use Windows' built-in tool, Disk Management. Or, your drive maker, Samsung, may have a free downloadable utility to make initializing the drive easy.
There's one other thing you should check. In your BIOS Setup screens the SATA port you are trying to use must be Enabled. If yours are not, change the setting so your BIOS can recognize the HDD unit.