My 2860n is running the latest firmware 3.8.2.2_VT3.

It works very well except my wireless data speeds between PCs on the network is very slow - about 1.1 MB/s. This isn't fast enough to stream an HD movie.
When I download a file online it comes much faster.
Both PCs are close to the router, I've tried all channels and it's on 11n mode only.
In the wireless LAN advanced settings there are quite a few options as below. Could these help? My settings are underlined.
Are there any settings in my PCs I should change? They're both running Windows 10 all updates.

Operation Mode Mixed Mode Green Field
Channel Bandwidth 20 20/40 40
Guard Interval long auto
Aggregation MSDU(A-MSDU) Enable Disable
Long Preamble Enable Disable
Packet-OVERDRIVETM TX Burst Enable Disable
Tx Power 100% 80% 60% 30% 20% 10%
WMM Capable Enable Disable
APSD Capable Enable Disable
Rate Adaptation Algorithm New Old
Fragment Length (256 - 2346) bytes 2346
RTS Threshold (1 - 2347) bytes 2347

Can you connect a PC hard wired for testing ?

Then you can test PC 1 with wireless a wired PC and the. Separately test PC 2 in the same way. Might show is one of the two is having difficulties.

Also try with channel bandwidth set to 20

Try setting the WMM Capable option you've shown there to Enable

And try different wireless channels - 2.4GHz can be quite busy so changing channels can often improve speeds.

One last thing is that in most environments (unless no wireless networks show when doing AP Discovery), I would set the Channel Bandwidth to 20MHz. I've personally found it will often give higher speeds on 2.4GHz than using 40MHz channels (due to interference / retransmissions).

anparkinson wrote: My 2860n is running the latest firmware 3.8.2.2_VT3.
Both PCs are close to the router, I've tried all channels and it's on 11n mode only.
In the wireless LAN advanced settings there are quite a few options as below. Could these help? My settings are underlined.
Are there any settings in my PCs I should change? They're both running Windows 10 all updates.

Operation Mode Mixed Mode Green Field
Channel Bandwidth 20 20/40 40

Change channel bandwidth to 20MHz, no point running 40MHz on 2.4GHz. Scan your house with WiFi Analyzer (free on Google Play Store) to find which channel is the least congested.
Which channel are you using? Remember only ever use 1, 6 or 11. If you anything else you'll be overlapping with other wireless networks and getting interference. http://www.metageek.com/training/resources/why-channels-1-6-11.html
Change operation mode to Green Field.
Finally, are there any cordless phones, microwave ovens or video senders near the router? Any of these will cause interference.