New DELL with faulty hardisk

I bought a new DELL INSPIRON 15R Laptop with the following specs
INTEL CORE 1GHZ Processor
1TB 5400 RPM Hardisk
It gave me problems right away
 1) Excruciatingly slow start   ( proprietress attributed that to system setting by DELL  !  Even compared  it to ASUS computer which she said was even slower ! )
2) Computer hanged when multiwindows are opened
3) etc , etc


I sent it back to the shop after making some complaints through the phone . After waiting for a week ( sat - sat ) with no calls from the shop , my husband dropped in and found that it was  ready !  The business concern aims to keep high standards of service , is this a joke ? And this happened after we emphatically mentioned that we wanted  it back the soonest , we even called up once to remind them.  One thing for sure , the proprietress must have felt guilty about her over-confident words for she avoids seeing us ! She has been always at the front desk meeting all customers .


Our returned laptop has a new hardisk ! I am really interested to know how often a new computer has a failed or faulty hardisk ? Isnt the hardisk the " brain " and therefore the most important part of the laptop ? Is it enough  to warrant a new laptop ?  I would be happy if any readers can offer some suggestions !