A second drive can make certain situations faster. decompressing a large file from one drive to another is where I notice it works faster with two drives. Video converting might run faster.
Overall just adding a second drive won't make any difference.
I had the same thought and this is coming up as the first result in Google.
I disagree with the other answers; it can make XP faster without reinstalling. This might be useful with all the old hard drives knocking about.
I have just added a spare second hard drive to a fairly powerful computer; dual core, plenty of RAM, plenty of hard drive space.
Then moved the paging file to the new hard drive (Control panel -> System -> Advanced -> (Performance) Settings -> Advanced -> Change)
I timed it before and after. Booting is 10% faster, I think it should also make a bigger difference when a large number of programs are opened, but didn't test this.
Ten percent isn't a significant difference unless we're talking about a very long boot-up time. Moving your pagefile to another physical drive does increase performance... but 10% just doesn't sound like much.
Taken from XP Myths:
"If your PC has more then one physical hard drives you can enhance performance by putting the paging file on a different partition and on a different physical hard disk drive. That way, Windows can handle multiple I/O requests more quickly. When the paging file is on the boot partition, Windows must perform disk reading and writing requests on both the system folder and the paging file. When the paging file is moved to a different partition and a different physical hard disk drive, there is less competition between reading and writing requests. However, if you remove the paging file from the boot partition, Windows cannot create a dump file (Memory.dmp) in which to write debugging information in the event that a kernel mode Stop Error message occurs. This could lead to extended downtime if you must debug to troubleshoot the Stop error message. The optimal solution is to create one paging file that is stored on the boot partition, and then create one paging file on another partition that is less frequently accessed on a different physical hard disk if a different physical hard disk is available. Additionally, it is optimal to create the second paging file so that it exists on its own partition, with no data or operating-system-specific files. By design, Windows uses the paging file on the less frequently accessed partition over the paging file on the more heavily accessed boot partition. An internal algorithm is used to determine which paging file to use for virtual memory management."
They say go ahead and put that pagefile on the secondary drive... but also keep a pagefile on the boot drive as well.
I have just experienced the same thing when adding a second hard drive to my server. I installed a second SATA drive just to have the additional storage space. It is only a 320 gb 4200 rpm drive, but on boot I immediately noticed the difference.
This is an IBM Intellistation, M Pro running Windows 7 Ultimate which is a clean install with updates. The unit had been running a little sluggish to me, but when the second drive was added I couldn't believe the differenct. There has to be something that changed with access of the drive on the motherboard.
2. If the old drive is a few years old or older, then a new drive can make a difference. For example I had a 4 year old 250GB WD drive with an average read speed of 50Mb/s. I have a newer 500GB drive with an average read of 120Mb/s. Moving the pagefile to this new drive makes sense since it's faster. Copying files from a new drive to a new drive is much faster than copying to the old drive as it's slow read speed is a bottleneck.