You can use Raid 0+1 if your motherboard supports it.
Some people may shy away from Raid 0 due to no fault tolerance but if you were running a single large HD and that failed you'd have no fault tolerance then either.
Raid 5 is striping with parity.
Every time a block is written, a parity block gets written.
Therefore if one disk goes down, you can slap another one in and re-create the data from the parity blocks.
Remember if you run 4 disks in a raid 0 config then you are 4 times more likely to lose all of your data compared to a single disk. Lose one disk, and you lose all of the data on all disks.
You can have 4 seperate disks, but use them as one volume in windows. You can mount new disks under a folder on an existing drive letter.
It's debatable if you gain much performance on the desktop from raid 0 anyway. Hard drive benchmarks often look great, but frequently real world apps don't benefit. Often it's faster to have seperate disks so you can have one source and one destination. Then you can have your source material on one and write the output to another. Of course, I can't comment on the particular app you will be using maybe it will be different.
...to awnser your original question you should be able to have 4 disks in a raid 0 array, but it will depend on the capabilities of the raid controller.