Should have done your research first, that's a slim PC, and you bought a full-slot card, you need either a low profile card (7750) or a new case and probably PSU, you could do the case/psu for $100 or less, and the card would be less as well, just depends which way you want to go, here's some possibilities:
Case+PSU:
PCPartPicker part list /
Price breakdown by merchant /
Benchmarks
Case: Raidmax ATX-298WW ATX Mid Tower Case ($24.99 @ Newegg)
Power Supply: XFX 550W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply ($49.99 @ NCIX US)
Total: $74.98
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-10-11 00:39 EDT-0400)
Or a low profile 7750 for $100 after rebate:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814202002
Low profile 7750's are overpriced, i'd say the case/psu upgrade is a much better route to take.