Thats similar to asking - "if I have an IDE hard disk, and I attach a DVD-ROM drive , will it slow down the performance."
The answer in both the cases is NO! Both have no relation to each other's performance. You are merely adding another storage device to your storage subsystem. You are meant to be able to add as many disks as the motherboard can support and make use of it !
anishcool said:
Yes it is possible. The files located on the IDE HDD will obviously open slower than those located on the SATA drive.
Another misconception is that SATA is drastically faster than IDE/PATA drives. The truth is, the SATA-1 spec merely added a faster bus compared to the PATA UATA-133 spec - that has only helped in burst speeds, i.e. data that is stored in the HDD's cache can be accessed all that much faster.
Ignoring the cache part of data transfer, internally both SATA and PATA drives have the same mechanical components giving both of them equal performance ! Features of the SATA spec such as TCQ/NCQ are what give SATA the upper hand - *IF* your motherboard supports it.