My Fathers desktop hard drive has decided to fail.

Upon checking it has a 7200rpm, SATA hard drive.
I have checked PC world and the likes and they have 7200rpm ones in stock but are 1tb in size. Will this be ok to use with XP?

Or shall we go for a 5400rpm 500gb hard drive?

Thanks in advance

For the OS drive you want as fast as possible. As such 7200RPM is the way to go for a mechanical boot drive.

Whilst 5400RPM are used in laptops, it's a compromise for their lower power use.

As for XP. As long as you have SP1 or newer installed, anything over 137GB should be compatible (notwithstanding any hardware limitations).

As above.

You can always partition the dive into x2 500gb.

Be aware that purchasing a 1Tb Drive you will really only be using somewhere in between 800GB - 1Tb the file format does not covert truly 1 to 1 its 1024 into 1.

Only letting you know so you don't think you have been had off.
Its normal to loose when formatting a New Drive.

Picked up a 1.5TB from PC World for £59.99 on offer.

Now as it's a clean install I am considering fitting Windows 7 (32bit). He mainly uses the PC for browsing.

If and how do I partition the drive? Due to the size I can see him only using 200gb.

You can partition at the point of installation. Install via the custom option and set the partition size around 200,000 MB to get a 200GB partition (204800MB if you want it exactly 200GB).

Will it matter if I partition only once?

Will mosy likley be fitting it tomorrow.

Sorry, only just seen this. No, it won't matter.

The unpartitioned space will appear in Disk Management as unallocated, but you wouldn't know from Windows Explorer that you weren't using the full capacity of the disk. As Mark suggests, you can always partition the extra capacity at a later date for data storage.