Traveling around London from Heathrow daily

I'd get the Oyster card. You will never be charged more than the one day travel pass no matter how many rides you take, and single rides are discounted. You can get the card price refunded at the end of your trip

Does it cover the Heathrow Express or the regular train?

You can buy an Oyster pay-as-you-go card at Heathrow upon arrival. It does not cover the Heathrow Express, but will cover most National Rail train services. See below: http://www.tfl.gov.uk/tickets/14869.aspx

Neither the Travelcard nor Oyster PAYG cover trains from Heathrow Airport to Paddington, either Express or Connect. The only route from Heathrow that they cover is the London Underground Piccadilly Line. This will get you into town but is a bit slow. I think also that the three-day Travelcard has been withdrawn. I would get a PAYG Oyster: there is a software function on it to ensure that you aren't charged more per day than you would have been if you'd got daily Travelcards. I have no idea why you're staying in a hotel at Heathrow for four days, though. Any price difference is seriously not worth the added travel costs and inconvenience compared to staying somewhere more central.

Curious why are you staying so far from the City Center?
Whatever savings you may have generated by staying outside London will be eaten up in transport and time lost traveling into and out of London.

I booked a hotel at the Heathrow Airport because of the price of 75L per night. I was told by the hotel it was very convient and only 10-20 mins away by train so I thought it would be fine. I am trying to find something central and am willing to pay a little more but everything I'm finding that has a decent review is alot more. If you any any recommendations I'd appreciate them.
Thank you

20 minutes by which train? A train is the Heathrow Express or Heathrow Connect. Quick travel but expensive! The tube is about an hour from Heathrow into London. Cheapest transport but that's two hours wasted on a commute. 74L? Lira? What IS your budget for lodging?

Sorry 75GBP. I was hoping to find something not more than 100GBP per night. I did find a hotel located in the docklands area but that seems pretty far away too. Right?

I assumed you were staying at Heathrow for business. If you are in London on vacation, then I agree with everyone else that Heathrow is too far out. I wouldn't base myself in the Docklands either. Here are a few hotels in central London in your price range, along with TA reviews: Luna Simone: http://www.lunasimonehotel.com/ Tripadvisor review: http://goo.gl/rIROa Lynton Hotel: http://www.lyntonhotel.co.uk/about.html TA review: http://goo.gl/LXdXE Ridgemount Hotel: http://www.ridgemounthotel.co.uk/prices TA review: http://goo.gl/qDu97 Cherry Court Hotel: http://www.cherrycourthotel.co.uk/index.html TA review: http://goo.gl/ognyq Vandon House: (the hotel website is currently down, so can't get the link to work) TA review: http://goo.gl/TTEpu Henley House: http://www.henleyhousehotel.com/index.html TA review: http://goo.gl/7jQvd There's also a really cheap B&B in North Harrow, which is outside central London (Zone 5). It is right around the corner from the tube station, though, and you could be in central London in 30 minutes. I wouldn't stay so far out on a first visit to London, particularly with only 4 days, but for some people it may be a good option. Tara's: http://www.taraslondonbandb.com/index.php
TA review: http://goo.gl/RxURB

Not to inundate you, but here are a few more options: Celtic/St Margaret's Hotel: http://www.stmargaretshotel.co.uk/W_e_l_c_o_m_e.html TA reviews: http://goo.gl/WmgEg Copthorne Tara: http://www.millenniumhotels.co.uk/copthornetarakensington/ TA reviews: http://goo.gl/oVgRH Hotel Meridiana: http://www.hotelmeridiana.co.uk/
TA reviews: http://goo.gl/ep8FF

You might also consider researching the airbnb website.
Here's an example of the type of place you can find; http://www.airbnb.com/rooms/60692 Have no clue about this place, don't know the owner, merely offering it as an example. I ssed it to find two stellar places in London last May and became a fan of the website. Love that there isn't any middle man. Once you express an interest the owner contacts you. Then you can ask all pertinent questions and get immediate responses. Is there an elevator? Can I make local calls? Will I have my own key? Etc., etc., etc. The hotels and b and b's recommended by OP's are good choices as well. STAY in London not at a Heathrow Hotel! Enjoy your trip. GREAT city.

I see you're already inundated with responses but since you named 75 pounds per night, I wanted to tell you to look at Vancouver Studios. I'm staying there for 8 nights in September and I e-mailed them to ask if they could give me a Rick Steves discount. They gave me 10% off my stay so I'm paying 75 pounds per night for a hotel room with a kitchenette. The hotel is in Bayswater, which looks far away from everything on a map but actually it's pretty central - that's how big London is!

A friend is staying in London in August and using university accommodation. She got a good deal on a room with bath at University College London. It is in Bloomsbury and so is close to the British MUseum as well as transportation to other parts of London. Costs are cheaper than hotels and some include breakfast. There are Halls of Residence all over London, check out the website www.Londonuniversityrooms.co.uk. Rooms are available until end of September.